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UBC Theses and Dissertations

Structure and properties of copper infiltrated iron. Krantz, Tibor 1964

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STRUCTURE AND PROPERTIES OF COPPER•INFILTRATED IRON  by  TIBOR KRANTZ  A THESIS SUBMITTED IN,PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE. DEGREE OF MASTER OF APPLIED SCIENCE  i i i t h e Department of METALLURGY  We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e required standard  Members o f t h e Department o f M e t a l l u r g y  THE UNIVERSITY OP BRITISH COLUMBIA  A p r i l , 1964  In presenting  t h i s thesis i n p a r t i a l f u l f i l m e n t of  the requirements f o r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make I t f r e e i y available f o r reference and study.  I further agree that permission  for. extensive copying of t h i s thesis f o r scholarly purposes, may granted by the Head of my Department or by his  be  representatives.  It i s understood that copying or publication of t h i s thesis f o r f i n a n c i a l gain s h a l l not be allowed without my written permission.  Department of  .  Metallurgy  The University of B r i t i s h Columbia, Vancouver 8, Canada. Date  ABSTRACT Two-phase c o m p o s i t e have been p r e p a r e d by i n f i l t r a t i n g compacts w i t h l i q u i d  copper.  sintered iron  The e f f e c t s have been s t u d i e d o f i r o n p a r t i c l e  s i z e , m a t r i x mean f r e e p a t h , and t h e volume f r a c t i o n and m i c r o - h a r d n e s s o f t h e i r o n - r i c h c o n s t i t u e n t , on t h e t e n s i l e p r o p e r t i e s o f c o m p o s i t e s .  I t has been f o u n d t h a t t h e s t r e n g t h o f t h e c o m p o s i t e s i s r e l a t e d t o t h e amount o f s o l u t i o n h a r d e n i n g o f t h e i r o n component d u r i n g  infiltration.  The r e s u l t s o f t e n s i l e t e s t s have s u g g e s t e d t h a t t h e hardness o f t h e i r o n - r i c h c o n s t i t u e n t i s t h e dominant f a c t o r c o n t r o l l i n g y i e l d s t r e n g t h , u l t i m a t e t e n s i l e s t r e n g t h and e l o n g a t i o n .  However, t h e u l t i m a t e s t r e n g t h has been found  t o depend a l s o on t h e volume f r a c t i o n o f t h e h a r d c o n s t i t u e n t , and e l o n g a t i o n has a l s o been found t o be a f u n c t i o n o f t h e i n t e r f a c e a r e a .  iii  ACKNOWLEDGEMENTS  The a u t h o r wishes t o thank h i s r e s e a r c h d i r e c t o r , D r . J.A. Lund f o r h i s a d v i c e and a s s i s t a n c e i n t h e i n t e r p r e t a t i o n o f t h i s r e s e a r c h .  He a l s o  wishes t o e x p r e s s h i s t h a n k s t o D r s . L . C . Brown and E. T e g h t s o o n i a n and t o o t h e r f a c u l t y members and f e l l o w graduate s t u d e n t s f o r h e l p f u l d i s c u s s i o n o f c e r t a i n points i n this  thesis.  The N a t i o n a l R e s e a r c h C o u n c i l g r a n t No.-A-1463, Defence R e s e a r c h Board Grant No. 7501-02 and Canadian Western P i p e M i l l s L i m i t e d F e l l o w s h i p i n Metallurgy provided f i n a n c i a l assistance. acknowledged.  This assistance i s g r a t e f u l l y  iii TABLE OF CONTENTS  Page  I.  INTRODUCTION AND SCOPE .  1  REVIEW OF LITERATURE . . . . .  II.  . . . ...  1.  Properties of Two-Phase iStructures  3  2.  Previous Work with Iron-Copper Composites .  6 . . . . .  8  Materials . . . . . . . . . . ;Specimen Preparation .. .;. a. Compaqtigg . . . . . . . . . . . . . b. Sintering. . . . . • . . . . . c. I n f i l t r a t i o n . ... . . . . . . . . . . . . . . . . 3. Density Measurement. ... 4. Tensile Testing . . . . . 5. Metallography . . . . . . . . a. Microhardness. .. . . v . . . • • b . Constitution, Mean Free Path, P a r t i c l e £jize . . .  8 9 9 10 11 12 13 14 15 15  EXPERIMENTAL PROCEDURE . . . . . . . . . . . .  . . .  1. 2.  v  III.  I n f i l t r a t i o n Time . . . ... I n f i l t r a t i o n Temperature:,. ... . . . Volume Fraction of I n f i l t r a n t . P a r t i c l e Size of Iron A d d i t i o n a l Experimental Results a. Constitution . . . . b. L a t t i c e Parameter of the IronRich Constituent . c . Cooling Rate E f f e c t s d. Properties of Bulk Copper-Rich A l l o y . . e. Relative P l a s t i c Deformation of the Two Constituents f . E f f e c t of Gas;; Pressure i n I n f i l t r a t i o n .  . . 17 • 24 . . . . . 30 33 . . . 37 37 . .  . . . . .  37 38 38  . . . . .  39 40  DISCUSSION 1. 2. 3.  •' Vl VI. VII.  17  EXPERIMENTAL RESULTS 1. 2. 3. 4. 5.  IV.  3  Porosity i n Composites. . Growth i n Iron Constituent P a r t i c l e s . . . . Effectoof Various Factors on the Tensile Properties of Composites. a. Matrix Mean Free Path and I n t e r p a r t i c l e Spacing of Iron. . ... . • b. Volume Fraction of Constituent . . ,• c. Hardness of the Iron Constituent » 4. Summary • • • • • • • • • • • • • •• • • • • • CONCLUSIONS. . . . . ... . . . . . . . . . . . . . . . . . . . . APPENDICES . . . . . . . . / . . ... . . ' . . . BIBLIOGRAPHY •  42 42 kk k6 47 48 5^ 5  4  55 60  iv  LIST OF FIGURES  Number  Page  1  Iron-Copper E q u i l i b r i u m Diagram  2  Effect; of I n f i l t r a t i o n  Time on I r o n  la Particle 19  S i z e ( I n f . Temp. 1150°C) 3  Effect of I n f i l t r a t i o n Constituents  4  Time on M i c r o h a r d n e s s o f t h e Two  ( i n f . Temp. 1150°C)  E f f e c t of I n f i l t r a t i o n  20  Time on S t r e n g t h  o f Copper  Infiltrated 21  I r o n ( I n f . Temp. 1150°C) 5  Sintered Iron Skeleton,  6  Specimen I n f i l t r a t e d  10 min. a t 1150°C, 300 X  22  7  Specimen I n f i l t r a t e d  120 min. a t 1150°C, 300 X  23  8  Specimen I n f i l t r a t e d  420 min. a t 1150°C, 300 X  23  9  E f f e c t o f I n f i l t r a t i o n Temperature on I r o n  10  300 X  26  P a r t i c l e S i z e ( i n f . Time 10 min.) E f f e c t o f I n f i l t r a t i o n Temperature on M i c r o h a r d n e s s of the Two C o n s t i t u e n t s  11  22  E f f e c t of I n f i l t r a t i o n Copper I n f i l t r a t e d  27  ( i n f . Time 10 min.)  Temperature on S t r e n g t h o f 28  I r o n ( i n f . Time 10 min.)  12  G r a i n Boundary P e n e t r a t i o n o f Cu i n t o Fe, 800 X  13  Mean Free Path v e r s u s  Volume P e r c e n t  29  o f the Copper. 32  Rich Constituent 14  Mean Free P a t h v e r s u s  Iron P a r t i c l e  15  Elongation versus  16  F r a c t u r e a f t e r Large P l a s t i c  17  B r i t t l e F r a c t u r e , 300 X  Size  Surface Area of Iron-Rich P a r t i c l e s Deformation, 150 X  •  35  .  36 41 41  LIST OF TABLES  Number  Page  1  I n f i l t r a t i o n Time  18  2  I n f i l t r a t i o n Temperature  25  3  Volume F r a c t i o n o f I n f i l t r a n t .  k  Particle Size.  .  •  . . .  31 3^  STRUCTURE: AND PROPERTIES OF COPPER INFILTRATED IRON  I.  INTRODUCTION AND SCOPE  I n f i l t r a t i o n ( a p p l i e d . t o m e t a l s ) i s a p r o c e s s by w h i c h t h e p o r e s o f a m e t a l powder compact a r e f i l l e d w i t h a r e l a t i v e l y low m e l t i n g - l i q u i d - m e t a l through the a c t i o n of c a p i l l a r y forces.  T h i s p r o c e s s y i e l d s a composite  m a t e r i a l w i t h a c o m b i n a t i o n o f p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f t h e components w h i c h cannot be a c h i e v e d b y any o t h e r method o f p r o c e s s i n g . The t e c h n i q u e i s c o n s i d e r e d a p p l i c a b l e t o s y s t e m s  1  where t h e  components have: a) b) c) d)  widely d i f f e r e n t melting points l i m i t e d mutual s o l u b i l i t i e s gqcjd " w e t t i n g c h a r a c t e r i s t i c s " ( d e f i n e d below) no i n t e r r a e t a l l i c compound, f o r m a t i o n w h i c h might with, f u r t h e r i n f i l t r a t i o n  interfere  There a r e few binary- m e t a l l i c systems w h i c h s a t i s f y , t h e s e r e q u i r e m e n t s f u l l y , and among them t h e iron-copper system i s p r o p a b l y t h e b e s t known. The m e l t i n g p o i n t s o f pure i r o n and copper a r e 1536°C and 1083°C respectively. p  The e q u i l i b r i u m d i a g r a m f o r t h e Fe-Cu system  i s g i v e n i n F i g u r e 1.  A t 1100°C. t h e s o l i d s o l u b i l i t y o f copper i n i r o n i s 8.5$ a n d , t h i s p r o p o r t i o n v a r i e s o n l y ' s l i g h t l y o v e r t h e range o f t e m p e r a t u r e w i t h w h i c h t h e p r e s e n t i n v e s t i g a t i o n i s m a i n l y c o n c e r n e d . -The s o l u b i l i t y o f i r o n i n copper a t 109^°C i s hfy, b u t d e c r e a s e s t o 2.3$> as a r e s u l t o f a . p e r i t e c t i c r e a c t i o n on c o o l i n g  --la  Figure 1.  Iron-Copper Equilibrium Diagram  -2  through t h a t temperature. increases again with  Above t h i s t r a n s f o r m a t i o n p o i n t the  -  solubility-  temperature.  I t i s a l s o seen f r o m t h e d i a g r a m t h a t no i n t e r m e t a l l i c compounds occur i n the iron-copper The  system.  " w e t t i n g c h a r a c t e r i s t i c s " o f t h i s system a r e good.  a n g l e o f m o l t e n copper w i t h s o l i d i r o n i s r e p o r t e d t o be z e r o ^ .  The  wetting  The d i h e d r a l  a n g l e , a ^ p a r a m e t e r d e t e r m i n i n g t h e i n t e r g r a n u l a r p e n e t r a t i o n o f t h e s o l i d by l i q u i d i s .27°  5  the  .  A c c o r d i n g t o K i n g e r y ^ t h e f o l l o w i n g s u r f a c e energy r e l a t i o n s h i p i s r e q u i r e d f o r w e t t i n g and d e n s i f i c a t i o n o f a porous body-by a l i q u i d ^ SV  >  ?LV >  >  %L  where the s u b s c r i p t s V, L and S r e f e r t o v a p o r , In  infiltrant  liquid and  solid respectively.  t h e case o f Fe-Cu t h e f o l l o w i n g n u m e r i c a l v a l u e s can be s u b s t i t u t e d  (fev = 1 9 5 0 ) > (tf5  LV r  1269) > (fss 6  =  850)^2$^ =  ' O 0 )\e erg (  cK  According t o these values the s o l i d - v a p o r i n t e r f a c e i s e l i m i n a t e d f i r s t  by  c o v e r i n g o f t h e i r o n w i t h m o l t e n copperj i n the second stage the p o r e s formed between t h e copper-cOated i r o n p a r t i c l e s a r e f i l l e d . boundary p e n e t r a t i o n , i s a p p a r e n t l y not f a v o u r a b l e .  The t h i r d s t a g e , g r a i n However, s i n c e  $~gg i s  a f f e c t e d by t h e a n g l e o f t h e boundary and by the s t r e s s d i s t r i b u t i o n i n the system, under c e r t a i n c o n d i t i o n s or i n c e r t a i n r e g i o n s t h i s t h i r d stage can cur a l s o .  oc-  -3  The s t r u c t u r e s o f a r t i f i c i a l two-phase composites w h i c h can be p r e p a r e d i  by i n f i l t r a t i o n can be c l o s e l y c o n t r o l l e d w i t h r e s p e c t t o phase d i s t r i b u t i o n and other parameters.  Thus.they l e n d t h e m s e l v e s w e l l , , i n p r i n c i p l e , t o s t u d i e s o f  the  d e f o r m a t i o n b e h a v i o u r o f m i x t u r e s of. d u c t i l e phases.  the  o b j e c t o f l e a r n i n g more about t h e p r o p e r t i e s o f s u c h m i x t u r e s t h a t t h e  p r e s e n t s t u d y was u n d e r t a k e n .  I t was p r i m a r i l y w i t h  Moreover, i t was hoped t h a t i t might be p o s s i b l e  t o e x p l a i n some o f t h e i n c o n s i s t e n c i e s i n t h e r e s u l t s o f p r e v i o u s i n v e s t i g a t i o n s w i t h c o p p e r - i n f i l t r a t e d i r o n compacts, s i n c e s u c h m a t e r i a l s a r e i m p o r t a n t commercially.  REVIEW. OF LITERATURE  I.  P r o p e r t i e s o f Two-Phase S t r u c t u r e s  The mechanism.of p l a s t i c d e f o r m a t i o n i n a two-phase a l l o y i s c o n s i d e r a b l y more complex t h a n i n a p o l y c r y s t a l l i n e s i n g l e phase a l l o y . the  Besides  u s u a l o b s t a c l e s t o d i s l o c a t i o n movement we f|£nd..' t h e i n t e r f a c e s and. t h e  second phase i t s e l f as a d d i t i o n a l . b a r r i e r s t o s l i p i n t h e m a t r i x .  Their  e f f e c t on t h e passage o f d i s l o c a t i o n s depends on t h e degree o f m i s f i t of t h e two l a t t i c e s , on t h e d i f f e r e n c e between t h e e l a s t i c p r o p e r t i e s . o f t h e two phases and on t h e amount and d i s t r i b u t i o n o f t h e two phases.  These parameters  v a r y f r o m system t o system, and may be v a r i e d w i t h i n one system by t h e c o n d i t i o n s of experiment.  I n m e t a l l u r g i c a l i n v e s t i g a t i o n s i t i s common  p r a c t i c e t o c o r r e l a t e t h e m i c r o - s t r u c t u r e w i t h t h e d e f o r m a t i o n b e h a v i o u r o f an a l l o y and. t o determine t h e f a c t o r s r e s p o n s i b l e f o r a c e r t a i n e f f e c t . o f t e n quoted parameters c h a r a c t e r i z i n g a two phase s t r u c t u r e a r e : a) b) c) d)  mean f r e e p a t h between jS'econd-phase p a r t i c l e s i n t e r p a r t i c l e s p a c i n g between second-phase p a r t i c l e s volume p e r c e n t o f t h e second phase hardness o f t h e two phases  The most  -  - k These parameters have been'examined b y o t h e r s i n d e t a i l f o r v a r i o u s twophase systems, and r e l a t i o n s h i p s have been d e r i v e d between them and t h e y i e l d s t r e n g t h , f r a c t u r e s t r e n g t h and d u c t i l i t y o f c o m p o s i t e s . ft Gensamer , s t u d y i n g ' t h e s t r u c t u r e s o f slow c o o l e d and s p h e r o i d i t i c  i  i  s t e d l s , proposed t h e r e l a t i o n s h i p  Cr =-A l o g (MFP) + B y  i n d i c a t i n g . t h a t t h e y i e l d s t r e s s depends on t h e l o g o f t h e mean f r e e MFP, t h r o u g h t h e c o n t i n u o u s phase ( f e r r i t e ) f r o m one h a r d phase  path,  (cementite)  p a r t i c l e ' or l a m e l l a t o another. 9  E d e l s o n and •• B a l d w i n  have s t u d i e d , t h e e f f e c t of . v a r i o u s second phase  a d d i t i o n s on t h e y i e l d s t r e n g t h of: copper. • They c o n c l u d e t h a t o n l y t h o s e p a r t i c l e s strengthen  copper which, f o r m a . f i r m bond w i t h t h e m a t r i x and t h a t  i n such cases t h e y i e l d s t r e n g t h a g a i n depends upon MFP. K r o c k ^ . found, t h a t i n W-NiFeW composites t h e d e f o r m a t i o n  character-  i s t i c s were independent o f MFP. The i n t e r p a r t i c l e s p a c i n g c r i t e r i o n appears t o p l a y an  important  r o l e i n d i s p e r s i o n hardening. Gregory and Grant  w o r k i n g w i t h f i n e o x i d e d i s p e r s o i d s i n aluminum  found t h a t t h e s t r e n g t h was p r o p o r t i o n a l t o t h e r e c i p r o c a l o f t h e o x i d e particle  spacing.  The c o m p a r a t i v e . v a l u e o f Gregory's r e s u l t s w i t h o t h e r two-phase structures i s doubtful since dispersion-strengthened  a l l o y s form a s p e c i a l  c l a s s o f m a t e r i a l s i n v o l v i n g low volume f r a c t i o n s and e x t r e m e l y f i n e p a r t i c l e s o f what i s u s u a l l y a . n o n - m e t a l l i c  dispersoid.  Due t o t h e s m a l l d i m e n s i o n s o f  t h e s e p a r t i c l e s t h e , i n t e r p a r t i c l e d i s t a n c e i s a c t u a l l y v e r y c l o s e t o t h e mean free  path.  There have been many attempts  t o c o r r e l a t e the mechanical p r o p e r t i e s  o f composites w i t h t h e volume f r a c t i o n o f t h e h a r d e r phase. reported i n t h i s regard are very  The r e s u l t s  controversial.  12 P i n e s and S u & h i n i n  d e r i v e d m a t h e m a t i c a l l y a r e l a t i o n s h i p between  s t r e n g t h -p'j and c o n s t i t u t i o n P = -Pi ( 1 - x )  2  + p x 2  2  + 2p x-(1-x) 12  where x i s . t h e volume f r a c t i o n o f t h e m a t r i x , and p , p x  2  and p  1  2  respectively  the s t r e n g t h s . o f t h e d i s c o n t i n u o u s phase, t h e m a t r i x and. the i n t e r f a c e .  Their  e x p e r i m e n t a l r e s u l t s o b t a i n e d a t t h e Cu r i c h end o f t h e Fe-Cu system appeared t o be i n good agreement w i t h t h e t h e o r e t i c a l Tesdorovich' "^ i n experiments 1  derivation.  w i t h b r a s s i n f i l t r a t e d i r o n found, t h a t  when t h e b r a s s content was d e c r e a s e d < from. 39 "to 20$ t h e y i e l d s t r e n g t h i n c r e a s e d from .21,000-psi  t o 57,000.psi w h i l e . t h e e l o n g a t i o n t o f r a c t u r e  d e c r e a s e d from 8 t o ^ . • E d e l s o n ^ found, t h a t d u c t i l i t y , u n l i k e YS, was a f u n c t i o n o f volume f r a c t i o n o f t h e phases. Ik •Kimura  reported that the f r a c t u r e strength of i r o n i n f i l t r a t e d  a 'Pb-Sn a l l o y remained l  with  e s s e n t i a l l y c o n s t a n t from 25$ t o 80$ o f i r o n and was c l o s e  to the bulk strength o f the matrix.  Above 90$ i r o n t h e composite  strength  increased. 15 Goetizel UTS  i n t h e range  w i t h t h e Fe^-Cu system found.no change i n composite of  72-82$  YS and  i r o n , but above t h a t t h e r e was a sudden i n c r e a s e i n  YS. from .28,000 t o 53,000 p s i . • Krock-'-O observed t h a t t h e d e f o r m a t i o n c h a r a c t e r i s t i c s o f W-NiFeW composite  were independent  20-42$ o f t h e m a t r i x phase.  o f t h e volume f r a c t i o n , a t l e a s t i n the .range o f  -6-  Previous Work w i t h Iron-Copper  Composites  A s i g n i f i c a n t volume of r e s e a r c h has p r e v i o u s l y been c a r r i e d out Fe-Cu composites because o f the f a v o r a b l e i n f i l t r a t i o n  characteristics  on  o f the  Fe-Cu system and because of i t s commercial importance and p o t e n t i a l i t i e s .  In what f o l l o w s no d i s t i n c t i o n w i l l be made between the processes infiltration  and  l i q u i d phase s i n t e r i n g ,  with the same mechanism and  . The  infiltration  s i n t e r i n g of iron-copper interest  driving force  are e s s e n t i a l l y  identical  involved.  of i r o n compacts with copper (and l i q u i d  powder m i x t u r e s ) began t o a t t r a c t  i n the l a t e n i n e t e e n  d u r i n g World War  s i n c e the two  of  phase  considerable  f o r t i e s a f t e r some i n i t i a l s t u d i e s i n Germany  II.  . K o p e c k i ? and K e l l e y 1  1 8  (1946), G o e t z e l  1 5  and W o r t h c o t t ^ (1947)  and  1  20 Smith  (1950) i n v e s t i g a t e d the procedures of i n f i l t r a t i o n and the e f f e c t  a l l o y i n g a d d i t i o n s and heat treatment on c o p p e r - i n f i l t r a t e d ? - i r o n purpose of e s t a b l i s h i n g properties.  with  c o n d i t i o n s t o o b t a i n the b e s t combination  the  of m e c h a n i c a l  In the second stage of development the b a s i c mechanism o f 1 (1955),  i n f i l t r a t i o n became the main t a r g e t o f s t u d i e s by E l l i o t (1959), E d e l s o n  9  and Whalen  •Although i t was  5  of  4  Kingery  (I962).  recognized  from the  start  1 15 19 21 ' ' ' that  alloying  1  between copper and i r o n took p l a c e , the s t r e n g t h i n c r e a s e due t o i n f i l t r a t i o n was at f i r s t a t t r i b u t e d t o "cementing" or a " h e a v y - a l l o y mechanism" s i m i l a r t o the one  operating  i n carbide-cobalt alloys  (Goetzel 5> 5 1  Northcott , 1 9  2  }  and  24 Schwartzkopf  ).  According,to  t h i s mechanism the hard p a r t i c l e s round o f f by  s o l u t i o n a n d r e p r e c i p i t a t i o n through the l i q u i d f i c a t i o n the two  phases are bonded.by cohesive  s t i l l a s u b j e c t of c o n t r o v e r s y  i n the  phase and  a f t e r complete ' s o l i d i -  forces only.  carbide-cobalt  system  T h i s mechanism i s itself.  - 7 -  As  shown by G u r l a n c V ^  of the c a r b i d e i n c o b a l t (38$  i n the WC-Co system t h e r e i s a l a r g e  by weight above the m e l t i n g p o i n t , 17$ below i t ) •  an a p p r e c i a b l e temperature dependence of the angle  s o l u b i l i t y , and a z e r o d i h e d r a l  c a u s i n g v e r y l a r g e changes i n t h e m i c r o s t r u c t u r e on c o o l i n g even by  quenching. it  solubility  While t h e r e i s no continuous  i s continuous  WC  skeleton at elevated  temperatures,  at o r d i n a r y temperature.  In the case  of Fe-Cu these parameters are e n t i r e l y d i f f e r e n t and  a p p r e c i a b l e s t r u c t u r e change i s expected  no  t o occur d u r i n g c o o l i n g .  I n r e c e n t y e a r s the emphasis has moved from the heavy a l l o y mechanism e x p l a n a t i o n t o a s o l u t i o n hardening  n o t i c e d d i f f u s i o n l a y e r s i n the i r o n p a r t i c l e s ^ however, he d i d not any  19^7  argument. . N o r t h c o t t as e a r l y as  attribute  s i g n i f i c a n c e t o them.  (1955)  Elliot^"  r e c o g n i z e d t h a t the d i f f u s i o n o f Cu  i n t o Fe would  e v i d e n t l y b r i n g about a change i n t h e m e c h a n i c a l p r o p e r t i e s o f the i r o n  and  t h a t the degree o f change would depend upon the amount o f copper d i s s o l v e d .  Resnhack  21  s o l u t i o n hardening  and  Teodorovich  13  22  '  were the f i r s t  (1961)  as the b a s i c mechanism of s t r e n g t h e n i n g .  t o advance  Rennhack observed  the h e a v y - a l l o y mechanism o p e r a t i n g a f t e r s a t u r a t i o n o f i r o n w i t h copper, which was  contrary t o observations  of others.  E d e l s o n and B a l d w i n ^ s t a t e d t h a t a l l "second .fphases"  (metallic,  non-  m e t a l l i c a n d . v o i d s ) e m b r i t t l e a-matrix because o f s t r e s s c o n c e n t r a t i o n , p r o v i d e d the second-phase i s s i g n i f i c a n t l y h a r d e r than the m a t r i x . they examined and found- b r i t t l e was  iron-copper.  .One  of the  Other workers have  composites observed  good d u c t i l i t i e s w i t h t h i s system which i n d i c a t e s t h a t the b r i t t l e n e s s i s not an i n h e r e n t property,-of the composite but depends on the a c t u a l m i c r o s t r u c t u r e .  - 8 -  The  a l l o y i n g o f the Fe component of the Fe-Cu system has "been found t o  have an important Schwartzkopf  effect  on the f i n a l p r o p e r t i e s of the i n f i l t r a t e d  product.  r e p o r t e d t h a t the a d d i t i o n of O.2570 carbon t o i r o n i n c r e a s e d  YS k>£ an a s - i n f i l t r a t e d product  61,200  from  to  72,900  p s i . and. the UTS  the  from  67,500 t o 76,100 p s i . A t present,, i n s p i t e of the extended commercial use development o f i r o n - c o p p e r  composites, the  p r o p e r t i e s of these a l l o y s are  . The  metallographic  and  practical  s t r u c t u r e and.the o r i g i n s of the  s t i l l matters of c o n s i d e r a b l e  structures of iron-copper  controversy.  composites have been  examined by almost every-worker i n , t h e f i e l d , but no one has  attempted;an even  q u a l i t a t i v e e v a l u a t i o n of the changes o c c u r r i n g d u r i n g i n f i l t r a t i o n ,  ! exception  with  the  27  of F r a n t z e v i c h  c o n c l u s i o n s based on these  , who  measured v a r i o u s parameters, but a r r i v e d a t  measurements. II.- EXPERIMENTAL PROCEDURE  1.  Materials The  m a t e r i a l s employed i n these. experiments were:  I r o n Powder A 100  l b . l o t o f Armco I r o n was  powders by F e d e r a l Mogul Co. airtight  container with a • The  for this  investigation.  des|drcant.  nominal c o m p o s i t i o n  C  atomized and  Mn  of t h e powder  P  S  was:  Si  s u p p l i e d as s p h e r i c a l I t was  shipped  i n an  no  - 9 -  The powder was standard  separated  i n t o 5 p a r t i c l e - s i z e f r a c t i o n s using a  screening procedure. • Sieve f r a c t i o n (Tyler)  E s t i m a t e d average p a r t i c l e s i z e (micron)  -100 . +150 -150 •+200 -200 .+270 -270 +325 • -325 The  s i e v e d f r a c t i o n s were p l a c e d i n t o p o l y e t h y l e n e bags.which were  f i l l e d w i t h n i t r o g e n and (-325  ' 127 . 89 63 kQ 25  s e a l e d o f f u n t i l r e q u i r e d . . Only the f i n e s t  mesh) underwent any v i s i b l e o x i d a t i o n d u r i n g the e x p e r i m e n t a l  Metallographic  e x a m i n a t i o n of the powders showed,that the  were n e a r l y p e r f e c t spheres a l t h o u g h  many were hollow.  .No  fraction  period.  particles  agglomeration  of the  p a r t i c l e s - was. observed.  Copper E l e c t r o l y t i c Tough P i t c h copper (copper was  obtained  i n the form of r o d , 3/8  were employed f o r i n f i l t r a t i o n . Limited  2.  The  -  99.92$  i n c h i n diameter. r o d was  min.,  oxygen - 0.04$)  Lengths of 2 ' l / 2  inch  s u p p l i e d by Western Copper M i l l s  (Noranda).  Specimen P r e p a r a t i o n  a.  .C ompact i n g The  compaction.  m a j o r i t y o f the T h i s method was  i r o n compacts were prepared  by h y d r o s t a t i c  preferred to conventional pressing i n r i g i d  because o f the more u n i f o r m d e n s i t y of the  product.  dies  - 10 -  -Since t h e i r o n powder p a r t i c l e s were o f s p h e r i c a l shape and were used i n narrow s i z e f r a c t i o n s , c o m p a c t i b i l i t y was v e r y poor and t h e a d d i t i o n o f a b i n d e r , a 1:1 m i x t u r e  o f i S c r y s o l and NH 0H, was added i n t h e r a t i o o f 1 drop p e r 4  • 30-40 g o f powder, and.thoroughly compacting.  mixed w i t h t h e i r o n by hand j u s t b e f o r e  - The mixture was p l a c e d i n a rubber, tube h" long,. 12 mm.. O.D.., w i t h  2 mm. w a l l thickness,, a n d - s e a l e d a t one end w i t h a rubber  stopper.  After  filling,  the o t h e r end o f t h e r u b b e r tube was a l s o s t o p p e r e d and t i e d w i t h a copper Three such bags were f i l l e d and p l a c e d a t one time  i n a steel hydrostatic  p r e s s u r e c y l i n d e r o f 2" I-.D.-and depth 6", which was t h e n f i l l e d c o n t e n t s of' the p r e s s u r e v e s s e l were compressed a t compacts were.3.5" l o n g and 0.4" diiameter.  wire.  20,000  to  with o i l .  30,000  The  p s i . - The  D e s p i t e t h e presence, o f a b i n d e r t h e  compacts were v e r y f r a g i l e and-many c o l l a p s e d d u r i n g h a n d l i n g .  Some specimens were p r e p a r e d from uncompacted powders.  In t h i s  case,  l o o s e powder was p l a c e d i n a 0.3" / molybdenum tube w i t h a . c l o s e d end ahd the. :  whole assembly was i n t u r n e n c l o s e d i n t o a q u a r t z tube and s i n t e r e d as described i n the f o l l o w i n g section.  b.  Sintering S i n t e r i n g was c a r r i e d out i n o r d e r t o g i v e t h e compact  sufficient  s t r e n g t h t o w i t h s t a n d f u r t h e r h a n d l i n g and machining.  The  f u r n a c e used f o r b o t h s i n t e r i n g and i n f i l t r a t i o n was an e l e c t r i c  r e s i s t a n c e t y p e , c o n t a i n i n g s i x , 12 mm. placed v e r t i c a l l y i n a c i r q i e centre  diameter  o f 5-5" d i a m e t e r .  "Globar"  ( S i C ) elements  The u n i f o r m h o t zone i n t h e  ( g r a d i e n t -less t h a n 10 degrees. C e n t i g r a d e ) was found t o be 3-5" l o n g .  Temperature c o n t r o l was p r o v i d e d . b y  a Honeywell c o n t r o l l e r w i t h a P t - P t 10 Rh  thermocouple' i n s t a l l e d i n t h e c e n t r e o f t h e u n i f o r m hot zone.  The s e t t i n g o f  the c o n t r o l l e r was a d j u s t e d d a i l y a c c o r d i n g t o t h e a c t u a l temperature  'measured  - 11 -  i n s i d e a.quartz tube s i m i l a r , t o t h e one used i n t h e experiments. temperature  The maximum  v a r i a t i o n i n s i d e t h i s tube was found t o be ± 4°C a t 1150°C.  A compacted b i l l e t  (or..the molybdenum, tube c o n t a i n i n g l o o s e powder) was  p l a c e d a t t h e bottom o f a . s e a l e d q u a r t z tube,' 20 mm. v e r t i c a l l y i n t o the furnace.  I.D., which was lowered  A l l s i n t e r i n g treatments were c a r r i e d out a t  1150°C f o r 10,minutes, w i t h a flow, o f cracked-ammonia through,the c o n t a i n e r . The r e d u c i n g gas i n l e t and an o u t l e t were p o s i t i o n e d i n such a way t h a t t h e compact was i n t h e actual- gas stream.  -The temperature  the p r e - s e t v a l u e a p p r o x i m a t e l y 5 minutes a f t e r  o f t h e specimen  reached  loading.  A f t e r s i n t e r i n g , t h e tube and c o n t e n t s were p u l l e d out from the' f u r n a c e and a l l o w e d . t o c o o l i n t h e a i r w i t h c r a c k e d a m m o n i a — s t i l l f l o w i n g .  .c.  I n f i l t r a t i o n •. I n f i l t r a t i o n . t o o k p l a c e i n a 12 mm.  end.  I.D. q u a r t z tube, s e a l e d a t one  A 12-15 g p i e c e o f copper r o d , p l u s some i r o n powder ( a p p r o x i m a t e l y 1.5 g)  were charg*ed i n t o t h e bottom, o f t h e tube.  The i r o n compact, by means .of a..small  h o l e driLked'.into i t near one end was susperiSed from.a  12" l o n g tungsten w i r e ,  t o t h e upper end o f which was a t t a c h e d a 1 " x 0.3" s t e e l c y l i n d e r . :  The l a t t e r  c y l i n d e r s e r v e d as a. core between two permanent magnets p l a c e d . o u t s i d e the q u a r t z tube. ,, By moving t h e s e magnets a l o n g the tube t h e core and t h e a t t a c h e d wire and powder  Compact  c o u l d be lowered-or r a i s e d i n s i d e the t u b e .  The.upper  (open) end o f t h e tube was connected t o a,vacuum forepump and t h e system.was  pumped  f o r ^several minutes t o o b t a i n a - s t a b l e vacuum o f a p p r o x i m a t e l y  65  microns.  - 12 -  A f t e r e v a c u a t i o n the tube was lowered v e r t i c a l l y i n t o the  furnace  w i t h the bottom supported 1 1/2." below the c e n t r e o f the u n i f o r m h e a t - z o n e . The specimen t o be i n f i l t r a t e d was then i n the p r o t r u d i n g p a r t  o f the t u b e .  The  tube was a l l o w e d t o come t o t h e r m a l e q u i l i b r i u m c d i r i n g which the copper melted and became saturated w i t h i r o n from the i r o n powder a d d i t i o n . was n e c e s s a r y which f i r s t  This  i n o r d e r t o prevent e r o s i o n of those p o r t i o n s o f the  saturation compact  came i n c o n t a c t w i t h the l i q u i d m e t a l ^ .  A f t e r 10 minutes the powder compact was lowered t o the bottom o f the tube,  submerged a p p r o x i m a t e l y 1/2 i n c h i n t o the molten p o o l , where i t was h e l d  f o r a measured t i m e ,  r a n g i n g . f r o m 10 m i n . t o ^20 m i n . , and was t h e n withdrawn  r a p i d l y i n t o the c o l d top h a l f of the t u b e . was v a r i e d from 1100°  The temperature  of i n f i l t r a t i o n  t o 1370°C.  When the i n f i l t r a t e d specimen had c o o l e d below " v i s i b l e r e d heat (approx.  650°C) the whole tube was p u l l e d out from the f u r n a c e and quenched i n  water.  3-  D e n s i t y Measurements  D e n s i t y measurements were c a r r i e d out on a l l specimens a f t e r  sintering  and a f t e r i n f i l t r a t i o n .  S i n t e r e d i r o n specimens were machined i n t o p e r f e c t  cylinders,  their  p h y s i c a l dimensions and t h e i r weights were measured, a n d . t h e s p e c i f i c weights were t h e n c a l c u l a t e d .  D e n s i t y was r e c o r d e d as a p e r c e n t  taken as 7.87 g / c c  iron.  for  of the  theoretical,  - 13  The d e n s i t y techniques.  o f i n f i l t r a t e d specimens was o b t a i n e d by l i q u i d - immersion  Carbon t e t r a c h l o r i d e was used as t h e l i q u i d medium because o f i t s  r e l a t i v e l y high s p e c i f i c gravity  ("1.54 g/cc) and good w e t t i n g c h a r a c t e r i s t i c .  • The c a l c u l a t i o n o f t h e t h e o r e t i c a l d e n s i t y was.based - o f t h e g i v e n specimen.  on.the s i n t e r e d  density  I t was assumed, and. l a t e r p r o v e n t h r o u g h c h e m i c a l and  m e t a l l o g r a p h i c a n a l y s i s , t h a t the Fe/Cu volume r a t i o a f t e r i n f i l t r a t i o n was the same as the Fe/pore r a t i o i n the s i n t e r e d specimen.  The d e n s i t y  o f copper was  t a k e n as 8.94 g/cc. f o r purposes o f c a l c u l a t i n g d e n s i t i e s as a p e r c e n t a g e o f theoretical.  4.  •Tensile  Testing A l l i n f i l t r a t e d compacts were machined i n t o t e n s i l e specimens o f t h e  shape and dimensions shown below.  Ifv  / ///  .0.3"  0.3" 2.5". 1.25"  -  - 14 -  Specimens were t e s t e d i n t e n s i o n on a n l n s t r o n t e n s i l e t e s t i n g machine, u s i n g . g r i p s s p e c i a l l y made f o r t h e button-head", specimens.  A l l t e s t s were c a r r i e d  out a t ambient t e m p e r a t u r e . - The s t r a i n r a t e used i n most cases was 0.2 aa^min ' a l t h o u g h 0.02 aaa^min'was used i n a few i n s t a n c e s .  .There were u s u a l l y 3  specimens t e s t e d f o r any g i v e n c o n d i t i o n (Appendix I I ) .  The  load-elongation  c u r v e s were r e c o r d e d .  The maximum l o a d was  c o n v e r t e d t o u l t i m a t e t e n s i l e s t r e n g t h , and y i e l d s t r e n g t h was d e t e r m i n e d by u s i n g a 0.2$ o f f s e t . E l o n g a t i o n s were measured on 1" gauge l e n g t h s , marked on t h e specimens b e f o r e t e s t i n g .  Metallography  One specimen f o r each c o n d i t i o n was examined m e t a l l o g r a p h i c a l l y . Three s e c t i o n s were, mounted- one t r a n s v e r s e t a k e n f r o m t h e t o p s h o u l d e r , and two  l o n g i t u d i n a l , exposing-both halves  o f t h e specimen f r a c t u r e .  I n o r d e r t o r e t a i n t h e sharp f r a c t u r e - e d g e formation  and t o p r e v e n t any r e l i e f  due t o t h e hardness d i f f e r e n c e o f t h e p h a s e s , l a p p i n g was c a r r i e d  out w i t h 6/c and 1/v diamond.  A f i n a l l i g h t p o l i s h was p r o v i d e d by L i n d e B  alumina. The  p o l i s h e d specimens were e t c h e d i n h'fo n i t r i c a c i d i n e e t h a n o l  produced v a r i o u s degrees o f b r o w n i s h c o l o r a t i o n i n t h e F e - r i c h c o n s t i t u e n t .  which The  d a r k n e s s o f t h i s c o l o r i n g was found, t o be r o u g h l y p r o p o r t i o n a l t o t h e amount o f copper i n t h e i r o n and served a s a q u a l i t a t i v e measure o f t h e e x t e n t o f diffusion.  - 15  The C u - r i c h m a t r i x was etched when r e q u i r e d w i t h a s o l u t i o n o f 5 p a r t s o f concentrated'NH OH, 4  a.  3 parts,  of  3 per  cent  H 0 2  2  and  5 parts H 0. 2  Microhardness Microhardness measurements were made on a Tukon t e s t e r w i t h a 145°  diamond pyramid i n d e n t e r .  Two l o a d s , 50 g and l O g , were used, h u t one l o a d  was used i n a g i v e n s e r i e s o f experiments.  only  Mean hardnesses were based on measure-  ments o f 6 t o 12 i n d e n t a t i o n s depending on t h e observed s c a t t e r .  I n t h e case o f  the i r o n - r i c h c o n s t i t u e n t wherein t h e hardness d i f f e r e d c o n s i d e r a b l y w i t h distance, from t h e m a t r i x ,  care was taken t o make i n d e n t a t i o n s on many p a r t i c l e s o f t h e  v a r i o u s shadings o f etched  b.  c o l o r t o o b t a i n an average hardness.  Cjonstitution,' Mean Free Path, P a r t i c l e The  ' \^  Size  measurement o f these parameters was c a r r i e d out by s t a n d a r d  lineal  28 analysis  on a Tukon t e s t e r equipped w i t h a f i l a r eye p i e c e and a t r a n s i t i n g  stage w i t h v e r n i e r adjustment. Traverses During  on t h e specimen were made i n t h r e e d i f f e r e n t d i r e c t i o n s .  a t r a v e r s e t h e number o f i r o n p a r t i c l e s was counted, and the' t o t a l  o f t h e l i n e and t h e . l e n g t h s  o f the copper i n t e r c e p t s were measured.  length  Transits  were made over 250 t o 300 i r o n p a r t i c l e s f o r each sample i n o r d e r t o o b t a i n a reliable  average. The  c o n s t i t u t i o n determination  is-based- on t h e premise t h a t t h e r a t i o o f  i n t e r c e p t s o f t h e two c o n s t i t u e n t s on a random l i n e i n a random  metallographic  section,-£_Cu , g i v e s t h e a c t u a l volume r a t i o o f the c o n s t i t u e n t s ' . £ Fe 2 8  \  The m a t r i x mean f r e e p a t h ,  i . e . t h e mean d i s t a n c e between t h e Fe  p a r t i c l e s , was o b t a i n e d by d i v i d i n g t h e t o t a l l e n g t h o f Cu i n t e r c e p t s w i t h t h e  - 16  -  number o f i r o n p a r t i c l e s i n t e r c e p t e d i n t h e t o t a l t r a v e r s e length;MFP = £ Cu %e The a v e r a g e • i r o n - p a r t i c l e s i z e was d e t e r m i n e d s i m i l a r l y , i . e .  d  Fe  =  L  t "  £cu  where  %e LLJ. i s t h e t o t a l l e n g t h o f t h e l i n e o f t r a v e l i s t h e l e n g t h o f Cu i n t e r c e p t s Njp i s t h e number o f i r o n p a r t i c l e s e  traversed  I t s h o u l d be n o t e d t h a t whereas t h e mean f r e e p a t h o b t a i n e d by t h i s method i s e q u a l t o t h e t r u e v o l u m e t r i c mean f r e e p a t h  the p a r t i c l e size  Fe i s  29 only two-thirds of the true p a r t i c l e diameter  f o r p a r t i c l e s of uniform  size.  I n t h e case o f non-uniform p a r t i c l e s , t h e mean s i z e measured m e t a l l o g r a p h i c a l l y i s a l s o a f u n c t i o n of the s i z e d i s t r i b u t i o n of the p a r t i c l e s .  The l a r g e r  s i z e d i f f e r e n c e between the p a r t i c l e s t h e g r e a t e r i s t h e p r o b a b i l i t y p a r t i c l e b e i n g t o t a l l y above or'.' b e l o w t h e p l a n e o f m e t a l l o g r a p h i c  of a small examination.  S i n c e the apparent p a r t i c l e s i z e measured m e t a l l o g r a p h i c a l l y i s i n v e r s e l y portional  i s the  pro-  t o t h e number o f p a r t i c l e s s e c t i o n e d by a random p l a n e , a r e d u c t i o n  i n t h e number o f t h e p a r t i c l e s would l e a d t o an i n c r e a s e i n t h e apparent s i z e . Thus, i n t h e case where some p a r t i c l e s o f i n i t i a l l y u n i f o r m expense o f o t h e r s d u r i n g i n f i l t r a t i o n , i s observed m e t a l l o g r a p h i c a l l y .  s i z e , grow a t t h e  an apparent mean p a r t i c l e - s i z e  increase  I n f a c t , t h e t r u e mean d i a m e t e r i s d e c r e a s i n g ,  a t l e a s t up t o t h e p o i n t where some p a r t i c l e s d i s a p p e a r  completely.  However, s i n c e t h i s study was concerned o n l y w i t h r e l a t i v e changes o f the p a r a m e t e r s , t h e d i a m e t e r v a l u e s used t h r o u g h o u t t h i s work have n o t been c o r r e c t e d t o a l l o w f o r t h e above e f f e c t s .  -.17 -  III.EXPERIMENTAL RESULTS  A l l e x p e r i m e n t a l d a t a and r e s u l t s a r e summarized i n Appendices  !•  I I and I I I •  I n f i l t r a t i o n Time  Specimens p r e p a r e d from were i n f i l t r a t e d f o r 10,  60,  120,  200 x 27O mesh i r o n powder p r e s s e d a t -"50,000 p s i . 200,  500-and U20 minutes a t 1150°C.  The  parameters  o f t h e m i c r o s t r u c t u r e and t h e m e c h a n i c a l p r o p e r t i e s of. r e p r e s e n t a t i v e s of t h e s e i n f i l t r a t e d specimens  are g i v e n i n T a b l e 1.  .The r e p r o d u c i b i l i t y o f t e n s i l e t e s t  r e s u l t s f o r each of the c o n d i t i o n s r e p r e s e n t e d i n T a b l e 1. may be o b s e r v e d . i n Appendix-'II.  Only those specimens  f o r w h i c h complete m e t a l l o g r a p h i c s t u d i e s  were c a r r i e d out have been i n c l u d e d i n T a b l e 1. The f o l l o w i n g o b s e r v a t i o n s can be made on t h e b a s i s o f t h e s e measurements: a.  The i n f i l t r a t e d d e n s i t y (98..2$ ; o f t h e o r e t i c a l on t h e average) i s independent o f t h e time o f i n f i l t r a t i o n .  b.  The Fe/Cu r a t i o , based on m e t a l l o g r a p h i c a n a l y s i s i s a l s o e s s e n t i a l l y constant.  c.  The apparent i r o n - p a r t i c l e s i z e i n c r e a s e s . r a p i d l y i n t h e e a r l y p e r i o d s o f i n f i l t r a t i o n ( F i g u r e 2). T h i s growth l a t e r slows down and a f t e r . 5 hours has e s s e n t i a l l y ceased.  d. • The mean f r e e p a t h a l s o a p p e a r s . t o i n c r e a s e w i t h . t i m e as a n a t u r a l consequence o f i r o n - p a r t i c l e growth- however,, 'tfjae e f f e c t u o f the i n i t i a l d e n s i t y , w h i c h v a r i e d t o a c e r t a i n degree, i s superimposed on t h i s e f f e c t and t h e t r e n d i s not o b v i o u s . e.  The m i c r o h a r d n e s s . o f t h e c o p p e r - r i c h m a t r i x . i s e s s e n t i a l l y c o n s t a n t w i t h i n f i l t r a t i o n . t i m e , whereas t h e hardness o f the. i r o n c r i c h c o n s t i t u e n t i n c r e a s e s r a p i d l y and. l i n e a r l y up t o ^ 5 hours where i t • suddenly l e v e l s , o f f ( F i g u r e  5).  TABLE 1 I n f i l t r a t i o n Time ( I n f . a t 1150°C) 200 x 270 I r o n Powder  Inf. Time min.  • Start Dens.  Inf. Cu c o n t e n t Dens. • G a l e Met.  1 •  ••1',  -  Fe Ratio "Met/Calc P a r t S i z e Sieve", Met  A  R a t i o 'Int. Mean Met/ . Part. •Free S i e v e Sp$ce P a t h  A  Hardness** Fe Cu VHN VHN  YS psi  UTS psi  E  3pec.  Wo.  A  1.05  63  43.8  0.70  5 8 . 7 ~ 14.9  103  -  19pW  38,500  45  40  19.6  0.88'  63  48.7  0.77  60.5  11.8  122  118  20p00  39J-00  9. 4  28  21.5  21.3  0.99  63  50.2  0.80  63-9  13.7  137  117  2&j200  45^00  7.0  31  97-8  22.7  19.9  0.88  63  52.6  O.83  65.7  13.1  169  110  42p00  52,000  5.0  67  79.5  98.3  20.5  19.6  O.96  63  53-5  O.85  66.5  13.O  204  117  54,700  62700  3.5  300  77.2  98.5  22.8  25.4  1.11  63  53.9  0.86  72.2  18.3  203  112  55^00  64,700  4.0  89  420  75.0  98.2  25.0  24.0  O.96  63  52.9  0.84  69.7  16V8 • 2067 111  56P-00  66900  1.0  59  0  70.7  10  77.7  98.0  22.3  60  78.5  98.4  120  77.3.  200  Abbreviations  -  74.6  &  i n t h e column h e a d i n g s f o r T a b l e s 1 t o 4  A Inf..- i n f i l t r a t i o n • Fe~ c o n t e n t o b t a i n e d m e t a l l o g r a p h i c a l l y Dens.- d e n s i t y ,•^,50 g load C a l c - v a l u e c a l c u l a t e d f r o m d e n s i t y measurements M e t a l s Handbook 1948, p. 432 "Dead S o f t " Met. - v a l u e o b t a i n e d t h r o u g h m e t a l l o g r a p h i c measurements Armco I r o n Int.part.space. - i n t e r p a r t i c l e spacing,  Time, m i n u t e s i  F i g u r e 2 . E f f e c t o f I n f i l t r a t i o n Time on I r o n - P a r t i c l e S i z e ( a p p a r e n t ) ( I n f . Temp. 1 1 5 0 ° C )  \o •  Figure 3 •  E f f e c t of I n f i l t r a t i o n ( I n f . Temp. 1150°C),  Time on M i c r o h a r d n e s s of the Two  Constituents  I  10  I  60  F i g u r e h.  1  120  1  180  1  2k0 Time, minutes  E f f e c t of I n f i l t r a t i o n Time on Strength.oof ( I n f . Temp. 1 1 5 0 ° C ) .  1  300  I  36O  I  k20  I  ''j  i  Copper I n f i l t r a t e d I r o n  1  ' £2  - 22 -  Figure  5-  Figure 6.  Sintered Iron Skeleton,  300  Specimen I n f i l t r a t e d 10 min. x.  .300  x.  a t 1150  C,  - 23 -  Figure 8 .  Specimen I n f i l t r a t e d 420 min. at 1150°C, 300 x.  -  24  f.  Both y i e l d and t e n s i l e s t r e n g t h s ( F i g u r e k) i n c r e a s e s l i n e a r l y w i t h time up t o 3 h o u r s . o f i n f i l t r a t i o n a f t e r w h i c h t h e r a t e s of i n c r e a s e drop t o c o n s i d e r a b l y l o w e r v a l u e s .  g.  The d u c t i l i t y measured as e l o n g a t i o n t o f r a c t u r e d e c r e a s e s w i t h i n c r e a s i n g time of i n f i l t r a t i o n .  -  Micrographs, o f a s i n t e r e d i r o n s k e l e t o n and o f specimens i n f i l t r a t e d f o r 10,  2.  120 and 420 minutes are g i v e n i n F i g u r e s 5,  Infiltration  6, 7  arl  d- 8 r e s p e c t i v e l y .  Temperaturer  Specimens s i m i l a r t o the ones u s e d i n t h e p r e v i o u s t i m e s e r i e s were i n f i l t r a t e d f o r 10,minutes a t 1100, are p r e s e n t e d  1150,  1260  i n Table 2 and i n F i g u r e s 9,  10,  and 1370°C. and 11.'  The p r o p e r t i e s  Additional tensile  obtained data  are c o n t a i n e d i n Appendix I I . The  o b s e r v a t i o n s are b a s i c a l l y the same as i n the time s e r i e s .  i n f i l t r a t e d d e n s i t y , (except a t the l o w e s t t e m p e r a t u r e ) ,  The  t h e volume r a t i o of  the cconstmtuents and the hardness o f the C u - r i c h m a t r i x were independent o f the i n f i l t r a t i o n t e m p e r a t u r e , whereas the i r o n - p a r t i c l e s i z e , the mean f r e e path,'' t h e hardness o f t h e F e - r i c h q o n s t i t u e n t and the u l t i m a t e and y i e l d i n c r e a s e d as the i n f i l t r a t i o n temperature was w i t h i n c r e a s i n g temperature. was  increased.  strengths  D u c t i l i t y decreased  However, no l e v e l i n g o f f of a n y of t h e s e parameters  observed w i t h i n the temperature range i n v e s t i g a t e d .  I t was  a l s o observed t h a t specimens i n f i l t r a t e d a t 1100°C showed.a  . c o n s i d e r a b l y l a r g e r amount o f g r a i n boundary p e n e t r a t i o n t h a n t h e ones a t h i g h e r t e m p e r a t u r e s (see F i g u r e 12).  infiltrated  -At t e m p e r a t u r e s c l o s e t o the m e l t i n g p o i n t  the s u r f a c e t e n s i o n o f l i q u i d i s r e l a t i v e l y h i g h and the m o l t e n copper  layer"formed  around each F e - p a r t i c l e e x e r t s a s i g n i f i c a n t compressive f o r c e , w h i c h e f f e c t s t h e  iTss  °f the i  r o n  and. r e n d e r s g r a i n boundary p e n e t r a t i o n more f a v o r a b l e .  TABLE 2 I n f i l t r a t i o n Temperature (10 min) 200 x 270 I r o n Powder  Temp  Start. Dens.  Inf. Dens.  •*  •*  70.7  -  -  Cu c o n t e n t C a l c . Met.  $  -  Fe Ratio- Part S i z e Met/ Sieve Met. Calc.  A  A  Ratio Met,/ Sieve  I n t . Mean P a r t . Free Space, P a t h  A  7^.6  1.05  63 1+3.8  0.70  Hardness Fe Cu VHW VHN  YS psi.  UTS fJsl.  E  Io  Spec No.  A 14.9  103  0.74  58.7 61.0  14.3  118 110  -  19I00 38^00 45.0  lasoo 37P00  40 46  1100  78.3  96.8  21.7  23.5  1.08  63  1150  77-7  98.0  22.3  19.6=  0.88  63  48.7  0.77  6O.5  11.8  122  118 20p00 39^00  1260  7-7.2  98.3  22,8  19-7  0.86  63 51.3  0.81  63-9  12'. 6  118 36700 52,400  8.C  1370  76.9  97-8  23.1  20.9  0.91  63 50.1  0.80  63.3  13.2  140 165  111 53poo 60800  2.C 78  13.5  28  44  50 g l o a d A.S.M. M e t a l s Handbook 1948, p. 432 A b b r e v i a t i o n s - See T a b l e 1  1 ro 1  Apparent P a r t i c l e Size, microns  F i g u r e 10.  E f f e c t o f I n f i l t r a t i o n Temperature on M i c r o h a r d n e s s o f t h e Two C o n s t i t u e n t s - ( i n f . . Time 10 m i n . ) .  F i g u r e 11.  E f f e c t o f I n f i l t r a t i o n Temperature on S t r e n g t h o f Copper I n f i l t r a t e d . I r o n ( i n f . Time 10 min.)  - 29  Figure 1 2 .  G r a i n Boundary P e n e t r a t i o n F e , 800 x.  of Cu i n t o  - 30 -  Volume F r a c t i o n o f I n f i l t r a n t . Specimens were.made from. 200 x 270 mesh i r o n powder a t z e r o , 20,000 and  30,000 p s i . coimpactiig p r e s s u r e f o l l o w e d "by s i n t e r i n g . One o f two groups compacted a t each p r e s s u r e was i n f i l t r a t e d 120 minutes a t 1150°C. g i v e n i n Table 3-  f o r 10 minutes a t 1150°C, t h e o t h e r group f o r  The i n f i l t r a t e d p r o p e r t i e s and o t h e r r e l e v a n t d a t a a r e  R e p r o d u c i b i l i t y t e s t s are contained  i n Appendix I I .  E x a m i n a t i o n o f t h e s e r e s u l t s show t h a t :  1.  The  amoiEit  o f f i n a l i n f i l t r a t e d p o r o s i t y does not depend on t h e r a t i o  of t h e volumes o f t h e two c o n s t i t u e n t s i n t h e range o f 18 t o hCrfo copper. 2.  The apparent i r o n - p a r t i c l e s i z e a f t e r i n f i l t r a t i o n i n c r e a s e s w i t h an i n c r e a s i n g amount o f i r o n i n t h e i n i t i a l compact..  3.  The matrix.mean f r e e p a t h i n c r e a s e s l i n e a r l y w i t h the. volume f r a c t i o n of copper and t h i s r e l a t i o n s h i p i s n o t a f f e c t e d by t h e i n f i l t r a t i o n time ( F i g u r e 13).  .4.  The microhardness o f t h e i r o n c o n s t i t u e n t , and, t h e y i e l d s t r e n g t h , s t r e n g t h and e l o n g a t i o n of. t h e composite a r e i n f l u e n c e d by t h e time o f i n f i l t r a t i o n  (as n o t e d p r e v i o u s l y ) b u t a r e independent o f  t h e volume r a t i o o f t h e two c o n s t i t u e n t s and o f t h e mean f r e e p a t h between t h e h a r d ( i r o n r i c h ) r e g i o n s .  tensile  • TABLE 3 Volume F r a c t i o n o f I n f i l t r a n t ( I n f . a t 1150°C) 200 x 270 I r o n Powder  S t a r t I n f . Cu c o n t e n t Dens. Dens. C a l c . Met.. 4 i •* •*  Ratio Met/ Calc.  Parf Size S i e v e Met.e  A  R a t i o - I n t . Mean Met/ P a r t . Free S i e v e Space. P a t h  , -ft Hardness Fe Cu VHW VHW  YS psi.  A  UTS psi. 27,100  -E 1o  Spec. - No.  39-9  1.08  63  43.2  0.69  71.9  28.7  1*5  106  23,200  43T£S©  7-5  56  30.2  27.7=  0.92  63  ^7.9  O.76  66.4  18.5  148  105  23,000  32,400  5-5  59  98.0  22.3  19.6  0.88  63  48.7  0.77  60.5  11,8.  126  20,000  59AOO  9 A  28  60.2  98.U:  39-8  37-7  0..95  63  44.7  0.71  72.0  27.3  172  106  35,200  42,200  4.0  61 b  120  71.4  98.1  28.6  26.0  0.91  63  46,3  O.74...... "62.5  16.2  193  111  .45,600-- 50,700  2.0  66 b  min.  77,3  97.8  22.7  19.9  0.88  63  52.6  O.83  13.1  201  115  42,000  52,800  5.0  67  63.3  98.0  .36.7  u69.8  97-3  min.  77-7  Inf.  Inf. 10  L:  ;  ft 10 g l o a d A b b r e v i a t i o n s - see T a b l e 1  65.7  - 32 -  32 . 30 . 28.  26 , 2k.  22 , 20 18 16 Ik x!  -p  CH  12  10  I O  i n f . 10 min. a t 1150°C  ®  i n f . 120 man. a t 1150°C  6, 4  18 ' io  1  ±2 ' 2k  ' 26 ' 28  1  30 ' 32 ' & ' 3D  '  -39  4o ' ^  Volume pearcent o f copper c o n s t i t u e n t  F i g u r e 13.  Mean Free P a t h v e r s u s Volume Percent, o f the CopperRich. C o n s t i t u e n t .  '  - 33 -  4.  P a r t i c l e Size of Iron  Two  (using;30,000 p s i .  groups o f specimens were p r e p a r e d  p r e s s u r e ) from each o f the f i v e s i e v e f r a c t i o n s specimens was  i n f i l t r a t e d for,10 minutes,  The r e s u l t s  o f i r o n powder.  compacting  One  s e t pf  the o t h e r f o r 120,minutes, a t 1150°C.  o f t e s t i n g , t h e s e specimens are c o l l e c t e d  i n T a b l e 4.  Additional  t e n s i l e t e s t data appear;; i n Appendix I I .  •The f o l l o w i n g o b s e r v a t i o n s can be made: 1.  Iron-particle  growth (as a percentage  i n c r e a s e ) i s more pronounced f o r  the f i n e r p a r t i c l e s and l o n g e r t i m e s . 2.  The m a t r i x MFP  increases l i n e a r l y with increasing•iron-particle  size  f o r b o t h i n f i l t r a t i o n t i m e s . ( F i g u r e 14). .  The microhardness. o f the m a t r i x shows a-tendency decrease  i n the i r o n - p a r t i c l e  4. • The hardness  to increase with a  size.  of the i r o n - r i c h c o n s t i t u e n t d i d not change w i t h the  p a r t i c l e s i z e i n the. case o f 10 min.  i n f i l t r a t i o n , but i n c r e a s e d  c o n s i d e r a b l y w i t h d e c r e a s i n g . p a r t i c l e s i z e w i t h the l o n g e r i n f i l t r a t i o n time. 5.  No consistent:- v a r i a t i o n w i t h p a r t i c l e s i z e was. found i n the case o f y i e l d and t e n s i l e s t r e n g t h s .  6.  High d u c t i l i t i e s , up t o 25$ c o a r s e r powder f r a c t i o n s ductility The  (see Appendix I I ) were observed f o r the  w i t h s h o r t i n f i l t r a t i o n time, and  decreased r a p i d l y with decreasing p a r t i c l e s i z e  specimens i n f i l t r a t e d f o r 120 min.  this (Figure  a l l had low. d u c t i l i t y .  15).  TABLE 4 P a r t i c l e Size ( I n f i l t r a t e d a t 1150°C) Sieve Start. Inf. Cu c on t e n t F r a c t i o n Dens. Dens. C a l c . Met. mesh % •* •* •*  Ratio Fe Ratio Met./ P a r t . 3 i z e Met./ C a l c . S i e v e Met. . S i e v e A A  A  Mean Int. P a r t . Free Space P a t h A r  Hard ness Fe Cu VHN VHN  YS psi.  UTS psi.  E  £>pec. Jo.  -100 +150  75.8  96.9  24.2  22.3  0.92  127  81.0  0.64  104.2 2 3 . 2  148  92  20,900  41,300 2 0 . 0  50  -150 +200  77.3  97-7  22.7  23,2  1,02  .89  58.8  0.66  7 6 . 5 17.7  143  106  23,200  41,300 17.5  53  -200 +270  77-7  98.0  22.3  19.6  0.88  63  48.7  0.77  6O.5  11.8  149  126  20,000  39,100  -270 +325  75-4  97-5  24.6  24.0  0.94  48 3 7 - 9  0.79  ' 4 9 : 8 11.9  153  111  23,600  46,600 1 2 . 0  55  -325  74.0  97.5  26.0  .21.5  0.83  25  21.7  O.87  6.0  154  117  27,500  37,400  57  -100 ' +150  74.0  98.2  26.0  24.5  0.94..  127  92.7  0.73  122.5 30.2  140  95  Inf.  -200 +270  77-3  97.8  22.7  I8..2  0.80  63  51.7  0.82  6 3 . 3 11.6  201  115  42,000  52,800  5.0  67  120  -270 +325  76.2  97-9  23.8  25.3  1.06  48 40.9  O.85  ;54.-7 1 3 . 8  197  105  41,100  41,300  0.5  85  -325  79.8  99-2  20.2  21.5  1.06  25  34.3  1.37  229  125  40,200  40,400  0.5  86  Inf. 10 Min.  Min-  -10 g l o a d A b b r e v i a t i o n s - see T a b l e 1  27.7  43.6  9.3  9.4. 28  5.0  36,400 53,500 7-5  73  - 35  F i g u r e lk.  Mean F r e e P a t h v e r s u s I r o n - P a r t i c l e S i z e ( a p p a r e n t )  -  - 36 -  F i g u r e 15.  Elongation versus Surface Area of Iron-Rich (10 min. I n f i l t r a t i o n a t 1150°C)  Particles  - 37 -  A d d i t i o n a l Experimental  Results  a. • C o n s t i t u t i o n The  c o n s t i t u t i o n of each specimen was  t h a t the r e l a t i o n s h i p • ( F e / p o r e s ) j . ^ S  n  <  = •(Fe./Cu-)± f±±t.  i n absolute  In three  No.. o f spec.  cases the c o m p o s i t i o n was  higher  s i n c e the other two whereas the wet  samples, gave 4$ higher valuesy i . e .  analyzed  chemically.  Analyzed W.-i Cu (wet)  C a l c . w.$ Cu adjusted f o r 4$ d i s s o l v . F e  Cal.Vol,$Cu (pores deducted)  78.0 77-7 62,6 The  comparison o f  copper content by weight.  .Vol.$Fe  45 28 37  The  assumption  ones measured m e t a l l o g r a p h i c a l l y  i n d i c a t e d t h a t the l a t t e r , on the average o f 22 higher  bolds.  n  d e n s i t i e s c a l c u l a t e d on t h i s b a s i s w i t h the  1$  c a l c u l a t e d based on the  19.6 20.3 35-1  21.3 22.2 58.2  copper c o n t e n t s o b t a i n e d  22.7 26.0  '  .40.7  by c h e m i c a l a n a l y s i s are  methods g i v e only, the volume percent  o f the  expected  matrix.copper  a n a l y s i s i n c l u d e s t h a t copper which i s d i s s o l v e d i n the i r o n - r i c h  constituent.  b.  L a t t i c e Parameter o f the "Iron-Rich X - r a y d i f f r a c t i o n u s i n g FeKoC  obtained  from specimen No.  25  Constituent  r a d i a t i o n was  ( i n f . . 2 0 0 min.  c a r r i e d qut  at 1150°C).  The  on .powder  Debye-Scherrer  i  pattern revealed  complete s e t s . o f BCC  and FCC  the i r o n - r i c h phase c a l c u l a t e d from the BCC The  lines.  l i n e s was  The  l a t t i c e parameter of  found t o be a = 2.8668 R.  r e p o r t e d v a i f i f e ' f o r Fe(»c) i s a = 2.8606°Aj hence,-Ma. = 0.22$ due 2  s o l u t i o n of copper i n i r o n .  to  the  '-'38c.  C o o l i n g Rate E f f e c t s  Specimen No. 58 ( i n f . studies.  420'.min. a t 1150°C) was s u b j e c t e d  t o cooling rate  One s e c t i o n was t e s t e d a s - i n f i l t r a t e d ; i . e . the hot specimen'!: (1150°C)  was p u l l e d i n t o the c o l d p a r t o f t h e quartz  tube and a l l o w e d , t o c o o l w h i l e the  tt\be was sprayed e x t e r n a l l y w i t h water.  The  1000°C  other, two s e c t i o n s were annealed i n cracked  i n a tube f u r n a c e .  ammonia f o r 1 hour a t  One was water quenched from t h i s temperature, t h e other  IJ -  was furnace  cooled.  . The meahanical p r o p e r t i e s were found, t o be as f o l l o w s :  C o o l i n g Rate  YS p s i .  48,000 ,46.,300 28,700  water quench process c o o l furnace c o o l  UTS p s i .  59,600 49,200 39,700  As expected, t h e c o o l i n g r a t e a f f e c t s the m e c h a n i c a l p r o p e r t i e s . • However, t h i s e f f e c t i s not l a r g e i n the range o f h i g h c o o l i n g r a t e s . yield  strengths  similar.  o f the water quenched and p r o c e s s c o o l e d  .Therefore  I n p a r t i c u l a r , the  specimens are v e r y  i t can be assumed t h a t the p r o p e r t i e s . a t t a i n e d i n . t h e  experiments are not a p p r e c i a b l y  a f f e c t e d by minor changes i n c o o l i n g r a t e s  present from  specimen t o specimen (speed o f w i t h d r a w a l , weight o f specimen, e t c . ) .  d.  P r o p e r t i e s , of Bulk Copper-Rich A l l o y  For r e f e r e n c e and t e s t e d . placed  d a t a an i r o n - s a t u r a t e d copper a l l o y specimen was p r e p a r e d  T w e n t y - f i v e grams o f copper and 1 gram o f Armco i r o n powder were  i n a.hydrogen c l e a n e d  c l o s e d a t one end. i n t o 1the furnace  t h i n - w a l l e d m i l d s t e e l tube o f I.D. O.36O", welded  A f t e r evacuation  w i t h a fore-pump t h e tube was p l a c e d  f o r l / 2 hour a t 1150°C.  saturated with i r o n .  vertically  D u r i n g t h i s time the copper became  A f t e r t h i s the tube and c o n t e n t s were water quenched and  swaged i n two passes f o r a t o t a l r e d u c t i o n  of area  o f 6l%.  T h i s was f o l l o w e d by  - 39 -  a n n e a l i n g f o r 10-min. a t 1050°C. i n vacuum, and a w a t e r quench. .obtained on m a c h i n e d . t e n s i l e VHN  86  e.  specimens :were: YS  UTS  24,400  47,200  . R e l a t i v e P l a s t i c Deformation  Specimens No.  19. and No.  deformation p r i o r t o f a i l u r e  (25$  46,  E  o f the Two  30  Constituents  w h i c h showed c o n s i d e r a b l e p l a s t i c  and 13.5$  e'longation r e s p e c t i v e l y ) were examined  m e t a l l o g r a p h i c a l l y : t o o b t a i n the r e l a t i v e d e f o r m a t i o n  The  The p r o p e r t i e s  o f the two c o n s t i t u e n t s . .  i r o n - r i c h p a r t i c l e s " i n an undeformed specimen 'are s p h e r i c a l .  D u r i n g . t e n s i l e deformation  t h e y become e l o n g a t e d a l o n g t h e specimen a x i s .  phases deform-.the same amount, i . e . the i n t e r f a c e i s , coherent  during  the shape change o f any . i r o n p a r t i c l e s h o u l d f o l l o w t h e d e f o r m a t i o n  I f both  deformation, o f the. whole  specimen. •In o r d e r t o v e r i f y t h i s , i n t h e l o n g i t u d i n a l m e t a l l o g r a p h i c s e c t i o n o f each specimen 12 p a r t i c l e s -were,measured f o r , - t h e i r l o n g e r and s h o r t e r a x e s , and b.  These p a r t i c l e s , were chosen i n , t h e u n i f o r m d e f o r m a t i o n  distance fromthe fracture.  zone a t about l / 4 "  On t h e average o f 12 measurements t h e f o l l o w i n g . d a t a  were o b t a i n e d . Spec.  19 46  No.  '  a  .a  170 98  b  a/b  calc.a/b  121 80  1.41  1.40  1.225  .1.21  - ko -  The c a l c u l a t i o n o f a/b was.based on an e l l i p s o i d a l shape o f t h e deformed i r o n p a r t i c l e s . Volume. = where  a a  1.25 r 1.135 r  3 TFab  2  =  3 jFr  3  f o r specimen No..19 f o r specimen No. 46  The measured i r o n - p a r t i c l e e l o n g a t i o n d e t e r m i n e d i n t h i s , manner a f t e r f r a c t u r e a g r e e d w i t h i n I70 s t r a i n w i t h the ' t o t a l e l o n g a t i o n o f t h e c o m p o s i t e .  f.  E f f e c t o f Gas P r e s s u r e i n I n f i l t r a t i o n D u r i n g • i n f i l t r a t i o n o f specimen No. 6 2 c ( 2 h r s .  10th  a t 1150°C) a f t e r - t h e  and. 60th• minute t h e vacuum.:line was c l o s e d o f f and argon was l e t i n t o t h e  i n f i l t r a t i n g tube a t a p r e s s u r e s l i g h t l y above a t m o s p h e r i c .  The o v e r p r e s s u r e  was m a i n t a i n e d f o r 2. m i n u t e s , a f t e r w h i c h t h e vacuum was r e - e s t a b l i s h e d . -The f i n a l composite d e n s i t y , 98.257°, was a p p a r e n t l y n o t a f f e c t e d b y t h i s t r e a t m e n t .  - kl -  Figure 17.  B r i t t l e Fracture, 300 x.  - 42 -  IV. -DISCUSSION  1.  P o r o s i t y i n Composites  R e s i d u a l p o r o s i t y was samples. Semlak^ .of  found i n the m i c r o s t r u c t u r e s , o f a l l . i n f i l t r a t e d  S i m i l a r o b s e r v a t i o n s were made by E l l i o t r e p o r t e d l y obtained.dense specimens a f t e r  infiltration  l  , while Frantzevich  and  respectively.  t h e m a j o r i t y o f the specimens  n o t a b l e e x c e p t i o n o f specimens p o i n t o f copper.  1  .2. - 5 minute and. JO minutes  The amount o f p o r o s i t y i n t h e p r e s e n t s t u d y was for  17  infiltrated  infiltrated  q u i t e c o n s t a n t (1.8*0.4$)  under v a r i o u s c o n d i t i o n s , w i t h t h e  a t a temperature j u s t above the m e l t i n g  The l a t t e r specimens.were.less dense t h a n the o t h e r s (~3-57°  porosity).  . The most obvious e x p l a n a t i o n f o r p o r o s i t y i s t h a t i t o r i g i n a t e s entrapped gases. are  However, i n f i l t r a t i o n was  Other f a c t s  a l s o a g a i n s t the p o s s i b i l i t y t h a t gases desorbed from-Fe p a r t i c l e s by the  moving copper phase would c o l l e c t  In not  c a r r i e d out i n vacuum.  from  or r e a d s o r b i n the p o r e s .  the p r e s e n t i n f i l t r a t i o n procedure the i n f i l t r a n t  p r o b a b l y does  e n t e r the s k e l e t o n from the"bottom, upward but r a t h e r r a p i d l y from the  s i d e s toward.the specimen a x i s . '  T h i s assumption i s . based on.the poor heat  c o n d u c t i v i t y o f t h e c o l d compact which a l l o w s the o u t s i d e s u r f a c e s t o heat above the of  m e l t i n g p o i n t o f copper c o n s i d e r a b l y f a s t e r t h a n t h e c e n t r e .  This  i n f i l t r a t i o n would be e x p e c t e d t o t r a p gases a t t h e c e n t r e o f the  However, the d i s t r i b u t i o n o f t h e pores was random r a d i a l l y or a l o n g t h e specimen a x i s .  sequence  specimen.  found m e t a l l o g r a p h i c a l l y to.i be; cbmple.tely The pore s i z e v a r i e d from 2 t o 10 u.  - 4$ The between 10 and  amount o f p o r o s i t y was 420  i n f i l t r a t i o n had  The  Thus w i t h  observed f o r 37$  final  25$  o f copper the  The  shrinkage  However, s i n c e the  1.2$  same p o r o s i t y  o r i g i n o f r e s i d u a l p o r o s i t y i s not i s pronounced. .The  the  number o f pores i n one  plane could lead;to high  c l e a r , i t s effect'-on  premature f a i l u r e o f the  stress concentrations,  critical crack  specimen.  case w i t h . a l a r g e number  of  specimens, p a r t i c u l a r l y those w i t h a h a r d i r o n - r i c h c o n s t i t u e n t , , where the s t r e s s i n the m a t r i x i s h i g h and, thus, any On t h e . b a s i s  o f the  are  strengths  are'very l i t t l e e f f e c t e d  v a l u e s are a f f e c t e d . t o a l a r g e r e x t e n t , and  strongly affected.  S i m i l a r observations  hydro-  s t r e s s - r a i s i n g - e f f e c t is-, more  r e p r o d u c i b i l i t y , of experiments i t can be  t o a h i g h degree o f c e r t a i n t y t h a t y i e l d p o r o s i t y , the UTS  the  d i s t r i b u t i o n o f pores i s  s t a t i s t i c a l p r o b a b i l i t y of having a . c e r t a i n  - A c t u a l l y t h i s i s . b e l i e v e d t o be the  significant.  was  copper t h i s argument i s not w h o l l y s a t i s f a c t o r y e i t h e r .  e s s e n t i a l l y random but  static  of  d e n s i t y r a t i o f o r copper  s h r i n k a g e would account f o r  r i g h t magnitude.  of i n f i l t r a t e d m a t e r i a l  and  pressure  density.  a l s o been c o n s i d e r e d .  a s . f o r 23$  • A l t h o u g h the  nucleation  infiltration  p o s s i b i l i t y t h a t the pores r e s u l t p r i m a r i l y from the  p o r o s i t y , which i s o f the  properties  time o f  f a c t t h a t a c y c l i c v a r i a t i o n of e x t e r n a l  no e f f e c t on the  copper upon f r e e z i n g has  - 4,92$.  a f f e c t e d by the  minutes, which f u r t h e r weakens the argument f o r entrapped gases.  Mareudoucts a r i s e from the during  not  elongation  were made by E d e l s o n and  said by  values  9 Baldwin .  - kh Growth o f t h e I r o n - C o n s t i t u e n t  Particles  Pronounced growth o f some i r o n p a r t i c l e s was observed i n every s e t o f experiments.  I n a s s e s s i n g , t h i s growth-phenomenon r e f e r e n c e s h o u l d be made t o -i  s e c t i o n I I - 5 (b) o f t h i s t h e s i s w h i c h d i s c u s s e d t h e e f f e c t o f s i z e d i s t r i b u t i o n , on t h e "apparent" p a r t i c l e s i z e o b t a i n e d m e t a l l o g r a p h i c a l l y . P a r t i c l e growth i n c r e a s e d w i t h t i m e , w i t h t e m p e r a t u r e , w i t h f i n e n e s s . o f t h e o r i g i n a l i r o n p a r t i c l e s , and w i t h i n c r e a s e i n t h e volume f r a c t i o n o f - i r o n . . (see F i g u r e s 2 and 9 ) .  •During t h e f i r s t stage o f i n f i l t r a t i o n and l i q u i d phase s i n t e r i n g o f i r o n - c o p p e r , p a r t i c l e growth, sometimes v e r y e x t e n s i v e , has been observed b y many • 1 3 19 31 workers, ' ' '  Rennhack  pi  r e p o r t e d t h a t he observed t h e same phenomenon  but o n l y a t a l a t e r s t a g e , a f t e r complete s a t u r a t i o n o f i r o n w i t h copper had occurred. P r i c e ^ , s t u d y i n g t h e W-NiFeW system, a l s o observed e x t e n s i v e growth w h i c h he a t t r i b u t e d t o t h e p r e f e r e n t i a l d i s s o l u t i o n o f s m a l l e r g r a i n s t h a n lyt,),  (less  due t o t h e i r g r e a t e r c h e m i c a l a c t i v i t y , and r e p r e c i p i t a t i o n o f t h i s  excess s o l u t e onto t h e l a r g e r p a r t i c l e s .  However^, i t i s b e l i e v e d t h a t i n . t h e  p r e s e n t work such e f f e c t s c o u l d n o t p l a y an i m p o r t a n t  role.  The p a r t i c l e s i n  these experiments were i n i t i a l l y o f narrow, s i z e d i s t r i b u t i o n , were a l m o s t p e r f e c t spheres,  and were r e l a t i v e l y iLarge.  - E l l i o t e x p l a i n e d t h e growth b y t h e e x p a n s i o n o f i r o n due t o copper e n t e r i n g s o l u t i o n and by. t h e p r e c i p i t a t i o n o f excess i r o n f r o m However,.calculations  indicate  solution.  t h a t a t f u l l s a t u r a t i o n (870 Cu i n Fe by w e i g h t ) ,  i n t h e case o f 6 5 y t s d i a m e t e r p a r t i c l e s t h e l i n e a r s i z e i n c r e a s e , /I d, would be ^ 2 $ , w h i l e t h e observed maximum growth i n t h e p r e s e n t work was 22$. c l e a r l y suggests t h a t some s o l u t i o n - r e p r e c i p i t a t i o n  process  This  occurs, although the  - 45  -  d r i v i n g f o r c e f o r t h i s mechanism has not p r e v i o u s l y been e x p l a i n e d . S i n c e p a r t i c l e growth, i n these e x p e r i m e n t s and. i n most o t h e r  reported  s t u d i e s stopped a t about the same t i m e as the hardness increase*'"" > and s i n c e no growth was  observed w i t h presaturated p a r t i c l e s  1  i t i s reasonable  t o assume t h a t  the growth i s c o n t r o l l e d by the d i f f u s i o n o f copper i n t o i r o n , or by the degree of s a t u r a t i o n of the i r o n w i t h copper. On the b a s i s o f t h i s the f o l l o w i n g t e n t a t i v e mechanism i s o f f e r e d . stages o f growth are c o n s i d e r e d c o r r e s p o n d i n g  Two  t o two l a r g e l y d i f f e r e n t s l o p e s i n  F i g u r e 2. I n the f i r s t s t a g e , w h i c h i s v e r y r a p i d b u t does not account f o r a l a r g e volume f r a c t i o n o f the growth, copper p e n e t r a t e s  i n t o the i r o n t h r o u g h f a v o r a b l y  o r i e n t e d g r a i n b o u n d a r i e s and as a consequence the g r a i n s are f o r c e d a p a r t . i t was  r e p o r t e d by B r e d a s ^ , . i n v e r y s h o r t times  o f Cu which has p e n e t r a t e d the i r o n t h i s way which has d i f f u s e d d i r e c t l y i n t o the i r o n  The  second and more i m p o r t a n t  (2 min.  As  a t 1100°G) the amount  can be 5000 times l a r g e r t h a n t h a t  lattice.  suggested stag-e o f growth i s an  indirect  22 r e s u l t of l a t t i c e d i f f u s i o n .  I t has been d e t e r m i n e d by T e o d o r o v i c h  using  e l e c t r o n m i c r o s c o p y t h a t d u r i n g d i f f u s i o n o f Cu i n t o Fe, a K i r k e n d a l l e f f e c t p r o d u c e s a h i g h vacancy c o n c e n t r a t i o n a t the i n t e r f a c e s .  I t i s reasonable  to  e x p e c t t h a t these d e f e c t i v e r e g i o n s have g r e a t e r t h a n normal apparent i n t e r f a c i a l energy.  S i n c e the r a t e of d i f f u s i o n o f Cu i n t o Fe (as the e t c h i n g p a t t e r n s  i n d i c a t e ) v a r i e s f r o m p a r t i c l e t o p a r t i c l e and even w i t h i n one  particle,  the  apparent i n t e r f a c i a l energy must be assumed t o v a r y a l s o from one p a r t i c l e t o another.  T h i s i n t e r f a c e energy d i f f e r e n c e would r e s u l t i n a f l u x o f i r o n toward  the d e f e c t s u r f a c e s i n o r d e r t o reduce t h e i r e x c e s s e n e r g i e s .  This process i s  i n o p e r a t i o n o n l y as l o n g as the d i f f u s i o n r a t e o f copper i n the i r o n i s s i g n i f i c a n t . I n the case o f specimens w i t h h i g h volume f r a c t i o n o f copper, the growth r a t e i s p r o b a b l y due  t o the l a r g e r i n t e r p a r t i c l e  spacing.  lower  - 46 3 • E f f e c t o f V a r i o u s F a c t o r s on t h e T e n s i l e P r o p e r t i e s o f Composites.  a.  M a t r i x Mean Free P a t h '(MFP) and I n t e r p a r t i c l e S p a c i n g  of the Iron(IPS)  I n t h e p r e s e n t work t h e MFP was c o n t r o l l e d by c h a n g i n g t h e volume f r a c t i o n , o f t h e m a t r i x and t h e p a r t i c l e s i z e "of t h e i r o n . MFP range o f 6 t o  2°yc  By these methods a  was o b t a i n e d .  E x a m i n a t i o n o f t h e d a t a g i v e n i n T a b l e 3 and k and Appendix I I i n d i c a t e s t h a t t h e change o f MFP had no s i g n i f i c a n t e f f e c t on t h e y i e l d s t r e n g t h , t e n s i l e strength or elongation. I n those  s e r i e s o f t e s t s i n which major changes o c c u r r e d i n composite  p r o p e r t i e s ( e . g . i n t h e t i m e and t e m p e r a t u r e s e r i e s , T a b l e s l a n d 2) t h e MFP was essentially The  constant. IPS i s t h e average d i s t a n c e between t h e c e n t r e s o f two a d j a c e n t  rich particles.  iron-  F o r r e l a t i v e l y l a r g e - p a r t i c l e s , such as those used i n t h e  present experiments,  t h e IPS I s made up o f t h r e e components, t h e r a d i i o f each  of two p a r t i c l e s , and t h e s h o r t e s t d i s t a n c e between t h e i r s u r f a c e s .  This  latter  rdimensioni i s p r o p o r t i o n a l t o t h e mean f r e e p a t h , t h e e f f e c t o f which was discussed i n the previous section.  The sum o f t h e two r a d i i g i v e s t h e mean  p a r t i c l e s i z e , w h i c h was v a r i e d d u r i n g t h e e x p e r i m e n t s b y u s i n g powders o f v a r i o u s s i e v e f r a c t i o n s w h i l e t h e volume r a t i o o f t h e two phases was kept, constant.. C o n s e q u e n t l y , a d e c r e a s e i n p a r t i c l e s i z e a l s o meant a d e c r e a s e i n mean f r e e path.  The r e l a t i o n s h i p between these two parameters i s l i n e a r ( F i g u r e lk).  The v a r i a t i o n o f p a r t i c l e s i z e was about k f o l d , from diameter,  22yt  t o Qlyu  w h i c h i s e q u i v a l e n t t o a lk f o l d . i n c r e a s e i n s u r f a c e a r e a and a 50  f o l d i n c r e a s e i n t h e volume o f i n d i v i d u a l p a r t i c l e s p e r u n i t w e i g h t .  T h i s had  no apparent e f f e c t on t h e YS and UTS v a l u e s , t h e changes o f w h i c h were i n no way c o n s i s t e n t w i t h t h e p a r t i c l e - s i z e changes ( T a b l e k).  - kl  The  -  e l o n g a t i o n v a l u e s , however, showed a w e l l - d e f i n e d t r e n d a t . l e a s t i n  the s h o r t i n f i l t r a t i o n t i m e s e r i e s . e l o n g a t i o n d e c r e a s e d f r o m 20 t o  ";With a d e c r e a s e of t h e p a r t i c l e s i z e ,  the  5$.  I n s p i t e of the l a c k o f c o n f i d e n c e  which' i s p l a c e d i n a b s o l u t e  e l o n g a t i o n measurements, t h i s f a c t i s i n t e r e s t i n g s i n c e i n t h e s e t e s t s the YS UTS  remained p r a c t i c a l l y c o n s t a n t .  I t i s . p o s s i b l e t h a t , i f the work  r a t e i s low, l a r g e changes i n d u c t i l i t y are accompanied by K r o c k " ^ has  hardening  s m a l l changes i n  UTS.  suggested t h a t the s u r f a c e . o r i n t e r f a c e c o n d i t i o n a l o f the  h a r d phase' has a v e r y ' : c r i t i c a l e f f e c t on  ductility.  As has been a l r e a d y mentioned t h e s u r f a c e of t h e i r o n p a r t i c l e s found by T e o d o r o v i c h  and  was  to c o n t a i n a l a r g e excess concentration of vacancies.  In  the e x p e r i m e n t under d i s c u s s i o n , because o f the s h o r t . i n f i l t r a t i o n time i n v o l v e d (10 min.)  a u n i t a r e a o f i n t e r f a c e f o r any  approximately  the same amount o f d e f e c t s .  s i z e of p a r t i c l e should  contain  I f t h i s i s so, and i f the d u c t i l i t y i s  d e t e r m i n e d by c o n d i t i o n s . a t the i n t e r f a c e , t h e r e s h o u l d be a r e l a t i o n s h i p between t h e amount o f i n t e r f a c e i n a g i v e n specimen and. i t s d u c t i l i t y . two  parameters ( F i g u r e 15)  these  g i v e s a good i n d i c a t i o n ' o f the e x i s t a n c e o f t h i s  p r e d i c t e d r e l a t i o n s h i p ^ i r i v i e w o f the;aforementioned  b.  A p l o t of  experimental  limitations.  Volume F r a c t i o n o f C o n s t i t u e n t s I n t h e p r e s e n t e x p e r i m e n t s the volume " f r a c t i o n o f the i r o n c o n s t i t u e n t  was  v a r i e d f r o m 60 t o iQ^o.  . The  t e s t r e s u l t s reported i n Table 3 i n d i c a t e t h a t  the y i e l d s t r e n g t h and e l o n g a t i o n were not a f f e c t e d by the r a t i o of the  two  phases i n t h i s range although' t h e r e i s n o t s u f f i c i e n t d a t a t o p e r m i t f i r m conc l u s i o n s t o be drawn.  - 48  A t t e m p t s were made t o c o r r e l a t e the UTS  -  data w i t h values c a l c u l a t e d from  P i n e s equation: 1  P = P  x  F e  2  +• P  C u  (l-x)  2  + PFeCu ( - ) x  1  x  However,, n e i t h e r t h e s t r e n g t h of t h e i r o n - r i c h phase,. P p , e  a c c o r d i n g to the microhardness i n t e r f a c e , ^-peCW  a r e  known f  r  w h i c h qbanges w i t h time  r e a d i n g s , nor t h e s t r e n g t h o f t h e o  d i r e c t measurements.  m  iron/copper  Strength values calculated  by u s i n g PpeCu = 6 6 , 0 0 0 p s i _as> employed by P i n e s f o r t h e low-carbon i n t e r f a c e i n h i s c a l c u l a t i o n s , and P p c h a r t s f o r the given microhardness  e  iron/copper  'obtained from h a r d n e s s - s t r e n g t h  conversion  of fche i r o n phase, were about 8 , 0 0 0 - l g ) 0 0 0  higher than the experimental s t r e n g t h s .  psi  However, t h e s l o p e s o f p l o t s o f s t r e n g t h  v e r s u s t h e square o f t h e volume f r a c t i o n were n o t f a r from t h e c a l c u l a t e d s l o p e s . T h i s i n d i c a t e s c l e a r l y t h a t t h e volume f r a c t i o n o f t h e h a r d e r phase has some e f f e c t on the composite t e n s i l t e s t r e n g t h , even though i t i s much l e s s marked t h a n the e f f e c t o f i n f i l t r a t i o n  c.  time.  Hardness o f t h e I r o n C o n s t i t u e n t s I n the p r e s e n t s t u d i e s each s e r i e s o f expeifjLments gave c l e a r e v i d e n c e  t h e s o l u t i o n h a r d e n i n g w h i c h accompanied i n f i l t r a t i o n . e v i d e n c e was  the microhardness  The most d i r e c t  of the i r o n - r i c h c o n s t i t u e n t . .  I n t h e i n f i l t r a t i o n time s e r i e s of t e s t s t h e average m i c r o h a r d n e s s t h e i r o n i n c r e a s e d almost linq'aajly up t o 300 m i n u t e s where i t l e v e l e d o f f ( F i g u r e 3)»  But t h e m i c r o s t r u c t u r e p r o v i d e d d e f i n i t e e v i d e n c e t h a t t h e  iron  copper  p a r t i c l e s were not c o m p l e t e l y s a t u r a t e d w i t h Iron-. was  The d i f f u s i o n l a y e r c o l o r  o f d e c r e a s i n g i n t e n s i t y toward t h e c e n t r e o f each p a r t i c l e ( F i g u r e 7')•  of  of  . 4  9  -  A f t e r the longest, i n f i l t r a t i o n time s t u d i e d , &20 minutes, the p i c t u r e was  s i m i l a r b u t .with .leiss c o n t r a s t .  The obvious d i f f u s i o n l a y e r s had moved  somewhat deeper i n t o the p a r t i c l e s , F i g u r e s l i g h t l y reduced. the  8>, . the hardness d i f f e r e n c e had been •  Though s a t u r a t i o n o o f i r o n w i t h copper was  probably incomplete,  depth o f p e n e t r a t i o n had r e a c h e d an e q u i l i b r i u m v a l u e f o r the  infiltration  time employed.  The cause o f the a p p a r e n t l y sudden change o f d i f f u s i o n r a t e a f t e r 2 hours of  infiltration  i s not clear..  But the microhardness and the m e c h a n i c a l p r o p e r t i e s  need not be e x p e c t e d t o i n c r e a s e c o n t i n u o u s l y t o the p o i n t o f complete ? Other workers r e p o r t  26 >  t h a t . t h e hardness and s t r e n g t h v a l u e s of i r o n - c o p p e r  a l l o y s i n c r e a s e up t o 2 $ copper o n l y and t h a t they l e v e l o f f beyond concentration. comparable  saturation.  The:hardness  that  v a l u e s quoted f o r the 2$ copper a l l o y are i n f a c t  t o those observed f o r the i r o n phase a f t e r 2 0 0 minutes  infiltration.  S i n c e the b e h a v i o r of the y i e l d and t e n s i l e s t r e n g t h c u r v e s ( F i g u r e was  4)  e s s e n t i a l l y the same as t h a t o f the hardness of the i r o n - r i c h phase, i t i s  r e a s o n a b l e t o assume t h a t the s t r e n g t h p r o p e r t i e s a r e s o l e l y c o n t r o l l e d by the hardness of the i r o n phase or by the hardness d i f f e r e n c e . b e t w e e n the two  phases  a s suggested by Heheman-^. In  the p r e s e n t experiments the hardness o f the m a t r i x remained  essentially  c o n s t a n t , so t h a t the hardness i n c r e a s e o f the i r o n a l s o c o r r e s p o n d s t o the i n c r e a s e of hardness d i f f e r e n c e . .  The assumption t h a t the composite phase and not by the weaker i s i n t e r e s t i n g . .  s t r e n g t h i s c o n t r o l l e d by the s t r o n g e r Comparing  these experiments  matrix composite  YS 24,400 56,100  UTS 47,200 66,900  the n u m e r i c a l v a l u e s i n  -  i t can be  seen t h a t the s t r e n g t h e n i n g due  50  -  t o the i r o n phase i s c o n s i d e r a b l e .  The m e c h a n i c a l p r o p e r t i e s r e p o r t e d f o r Aicmco i r o n and d e t e r m i n e d f o r the i r o n - s a t u r a t e d copper a r e v e r y s i m i l a r . .  T h i s p r o b a b l y e x p l a i n s the  o b s e r v a t i o n t h a t a f t e r s h o r t i n f i l t r a t i o n times b o t h phases deformed s i m i l a r l y and f a i l e d a f t e r a r e l a t i v e l y l a r g e amount o f p l a s t i c f l o w ( 2 0 - 3 0 $ ) . .  The  f r a c t u r e - p a t h went t h r o u g h b o t h phases w i t h no apparent p r e f e r e n c e f o r . e i t h e r 16).  (Figure  •  Asr. d i f f u s i o n p r o g r e s s e d  w i t h i n c r e a s i n g i n f i l t r a t i o n time, the  l a t t i c e became more d i s t o r t e d ( s o l u t i o n h a r d e n e d ) , i t s s t r e n g t h . i n c r e a s e d i t s d u c t i l i t y decreased.  The h i g h y i e l d s t r e n g t h o f the i r o n p a r t i c l e s  i n c r e a s e d the s t r e s s n e c e s s a r y  iron and  effectively  f o r g r o s s p l a s t i c f l o w i n the m a t r i x , and as a  r e s u l t h i g h composite s t r e n g t h and low d u c t i l i t y were o b s e r v e d .  The  stress  system i n the matrix,becomes e s s e n t i a l l y t r i a x i a l when a u n i a x i a l l o a d i s a p p l i e d t o t h e specimen, and the s i t u a t i o n became s i m i l a r t o t h a t f o u n d , i n b r a z e d  joints.  Bredjas--^ r e p o r t e d t h a t i n Fe-Ag b r a z e d j o i n t s the n o t c h c o n s t r a i n t . f a c t o r ( g i v i n g the r a t i o o f the a c t u a l s t r e s s a t w h i c h p l a s t i c d e f o r m a t i o n b e g i n s yield  t o the  s t r e n g t h ) c o u l d be as h i g h as k f o r a c e r t a i n t h i c k n e s s o f the b i n d e r . A t a c r i t i c a l v a l u e o f t h e a p p l i e d s t r e s s , i n the l i m i t i n g case o f an  extremely  hard second phase, the specimen f a i l s i n a b r i t t l e manner w i t h t h e  f r a c t u r e g o i n g p r e f e r e n t i a l l y t h r o u g h the c o p p e r - r i c h phase or a l o n g the i n t e r f a c e (Figure  17).  - 51  I n t h e l i g h t o f t h e s o l u t i o n h a r d e n i n g mechanism many made d u r i n g t h e course o f t h e s e e x p e r i m e n t s can be e x p l a i n e d .  -  observations Since  diffusion  depends on t i m e , t e m p e r a t u r e and d i s t a n c e , i t i s o b v i o u s t h a t l o n g e r t i m e s and h i g h e r t e m p e r a t u r e s o f i n f i l t r a t i o n , as w e l l as s m a l l e r p a r t i c l e s , s h o u l d h i g h e r s t r e n g t h v a l u e s , i n good agreement w i t h  I t i s necessary  give  observations.  t o note t h a t i n t h e l i t e r a t u r e t h e r e p o r t e d v a l u e s o f  t h e s t r e n g t h o f copper i n f i l t r a t e d  i r o n a r e i n some c a s e s s u b s t a n t i a l l l y  t h a n t h o s e o b t a i n e d i n t h e p r e s e n t experiments".  higher  T h i s i s most l i k e l y due t o ph.  d i f f e r e n c e s i n t h e p u r i t y o f t h e i r o n used.  Schwartzkopf  found t h a t the  a d d i t i o n o f 0 . 2 5 $ g r a p h i t e t o Fe p r i o r t o i n f i l t r a t i o n i n c r e a s e d t h e composite y i e l d s t r e n g t h f r o m 6 l , 0 0 0 t o 7 2 , 9 0 0 p s i , and ; t h e . u l t i m a t e t e n s i l e from 6 7 , 5 0 0 t o 7 6 , 1 0 0 p s i .  strength  The i r o n used i n t h e p r e s e n t work was o f h i g h p u r i t y  r e l a t i v e t o t h e c a r b o n y l • a n d others-iron powders u s e d . i n much r e p o r t e d work.  experimental  -  4.  52  -  Summary In evaluating'the  d e f o r m a t i o n behavioor o f c o p p e r - i n f i l t r a t e d . i r o n  compacts one has t o b e a r i n mind t h a t few p r o p e r t i e s o f m e t a l s a r e as s e n s i t i v e t o c r y s t a l l i n e s t r u c t u r e as those a s s o c i a t e d w i t h y i e l d i n g and f l o w .  .There seems  t o be l i t t l e agreement i n t h e l i t e r a t u r e about t h e p r e c i s e dependence o f d e f o r m a t i o n b e h a v i o u r on t h e s t r u c t u r e o f a.two-phase a l l o y -  These systems a r e  u s u a l l y t o o complex, w i t h t o o many v a r i a b l e s i n v o l v e d , t o lend, t h e m s e l v e s t o m a t h e m a t i c a l c a l c u l a t i o n s d e r i v e d from s i m p l e models. •3h,  A d i s l o c a t i o n theory, approach t o two phase systems by L e n e l a relationship  YS =  /2% C  whereyc and JO  J  predicts  a r e t h e shear m o d u l i o f t h e  m a t r i x and o f t h e second phase p a r t i c l e s r e s p e c t i v e l y and % i s t h e mean f r e e 8 11 path.  E m p i r i c a l f o r m u l a e w h i c h have been proposed '  a l s o suggest t h a t "  composite s t r e n g t h i s p r o p o r t i o n a l t o t h e r e c i p r o c a l o f •  > MFP.  r e s u l t s o f t h e p r e s e n t s t u d y i n d i c a t e no dependence on MFP a t a l l . explanation f o r the apparently  Butjithe One p o s s i b l e  n e g l i g i b l e c o n t r i b u t i o n o f MFP t o t h e s t r e n g t h o f  t h e s e composites i s t h e "maS'king" e f f e c t o f o t h e r ' f a c t o r s , . l i k e s o l u t i o n c. h a r d e n i n g ' of ---the copper-£ich phase due t o i r o n and t h e h y d r o s t a t i c s t r e s s e s i n the m a t r i x r e s u l t i n g 'from t h e d i f f e r e n t t h e r m a l e x p a n s i o n c o e f f i c i e n t s o f t h e iron-and  c o p p e r - r i c h phases.  The e f f e c t f r o m MFP i n t h e range - s t u d i e d  contributes  p r o b a b l y l i t t l e t o t h e r e s i d u a l s t r e s s e s from t h e above mentioned two s o u r c e s . E d e l s o n and B a l d w i n c o n c l u d e d t h a t the" presence o f any second phase, i f 9  i t i s harder than the matrix,  s e r v e r l y e m b r i t t l e s an a l l o y .  p r e s e n t work a r e i n d i s a g r e e m e n t w i t h t h i s c o n c l u s i o n .  The r e s u l t s o f t h e  I t seems t h a t t h e r o l e  . o f t h e i n t e r f a c e a l t h o u g h secondary i n y i e l d s t r e n g t h c o n s i d e r a t i o n s , i s t o reduce d u c t i l i t y t h r o u g h p r o v i s i o n o f s t r e s s r a i s e r s i n t h e form o f vacancy concentrations  w h i c h a r i s e t h r o u g h d i f f u s i o n between t h e two components.  This  - 53 -  i m p l i e s t h a t . i t i s n o t t h e hardness o f t h e second phase w h i c h d e t e r m i n e s d u c t i l i t y as p r o p o s e d b y E d e l s o n b u t t h e degree o f p e r f e c t i o n of. t h e i n t e r f j a c e s and t h e degree o f c r y s t a l l i n e c o m p a t i b i l i t y Finally i t i s interesting  between t h e phases. t o note t h e many s i m i l a r i t i e s between t h e F e -  Cu c o m p o s i t e s o f t h i s work and t h e W-NiFeW composites o f K r o c k e t a l ^ . have h i g h d u c t i l i t i e s under c e r t a i n  Both  c o n d i t i o n s , t h e i r s t r e n g t h s a r e independent  of M F P and volume f r a c t i o n o f t h e m a t r i x and t h e i r s t r e n g t h s depend s t r o n g l y on the  r e l a t i v e hardness,': o r s t r e n g t h , o f t h e second phase.  - 54 -  V.  1.  The major s t r e n g t h e n i n g  CONCLUSIONS  c o n t r i b u t i o n i n copper i n f i l t r a t e d i r o n composites  i s t h e hardness d i f f e r e n c e between the i r o n c o n s t i t u e n t and the matrix.  Any p r o c e s s i n g  copper-rich  c o n d i t i o n s which increase t h i s d i f f e r e n c e  increase  the y i e l d and f l o w s t r e n g t h s o f t h e c o m p o s i t e . 2.  The t e n s i l e y i e l d s t r e n g t h o f the composite depends on the hardness o f t h e i r o n - r i c h c o n s t i t u e n t o n l y , and i s a p p a r e n t l y  independent o f t h e volume  f r a c t i o n o f t h i s c o n s t i t u e n t ( i n the range o f 6 0 - 7 8 $ ) , t h e p a r t i c l e  size,  and t h e m a t r i x mean f r e e p a t h between t h e p a r t i c l e s . 3»  The u l t i m a t e t e n s i l e  s t r e n g t h i s a f u n c t i o n o f the hardness o f the  constituent but i s apparently  iron-rich  a l s o a f u n c t i o n o f t h e volume f r a c t i o n o f t h i s  constituent. 4.  The e l o n g a t i o n t o f r a c t u r e  depends on t h e hardness o f t h e  c o n s t i t u e n t and on the a r e a o f the i n t e r f a c e 5.  iron-rich  between the two phases.  The growth o f i r o n p a r t i c l e s w h i c h o c c u r s d u r i n g i n f i l t r a t i o n i s the r e s u l t of s o l u t i o n  and r e p r e c i p i t a t i o n  of iron.  p r o c e s s i s b e l i e v e d to' be a K i r k e n d a l l of copper i n t o  iron.  The d r i v i n g f o r c e f o r t h i s  e f f e c t a s s o c i a t e d w i t h the  diffusion  -  VI.  55  -  APPENDIX I  Microhardness Testing  The  use o f m i c r o h a r d n e s s t e s t i n g i n powder m e t a l l u r g i c a l p r a c t i c e where  the m i c r o s t r u c t u r e i s a complex m i x t u r e d i m e n s i o n s i n v o l v e s a number of  of d i f f e r e n t c o n s t i t u e n t s of  small  difficulties.  I n o r d e r t o measure t h e hardness o f a g i v e n phase the i m p r e s s i o n must be  s m a l l enough t h a t t h e work hardened zone s u r r o u n d i n g  r e a c h the phase b o u n d a r i e s .  the i m p r e s s i o n does not  But the s m a l l l o a d s n e c e s s a r y f o r s m a l l i n d e n t a t i o n s ^5  l e a d t o r e l a t i v e l y .large e r r o r s .  B u c k l e r - ^ has f o u n d the f o l l o w i n g r e l a t i o n s h i p 1  between l o a d and r e l a t i v e e r r o r , a r i s i n g from a c o n s t a n t e r r o r ( A d = 0.5yO i n o c u l a r r e a d i n g , f o r two  g i v e n hardness r a n g e s : e r r o r jo  Load g  At VHN  100 50 10  100  A t VHN  + 2 +3 +10  S i n c e most of the e x p e r i m e n t a l  e r r o r s t e n d t o r a i s e the  h a r d n e s s , t h e hardness seems t o i n c r e a s e w i t h d e c r e a s i n g o b t a i n the s m a l l e s t e r r o r p o s s i b l e i n the p r e s e n t used i n p r e f e r e n c e .  T h i s was  800  +8 + 10 +30  load.  apparent In order  e x p e r i m e n t s , a 50 g l o a d  the maximum l o a d w h i c h s a t i s f i e d t h e  l a r g e and 1 0 ' g t h e s e two  I n c e r t a i n cases,-however, t h i s l o a d was  l o a d had t o be u s e d .  Microhardness readings  obtained  l o a d s on the same specimens compare:.in the f o l l o w i n g  way:  was  practical  ru/le t h a t t h e i m p r e s s i o n d i a m e t e r s h o u l d ;be not g r e a t e r t h a n l / 5 of the diamiter of the c o n s t i t u e n t .  to  too with  - 56 -  '  Cu r i c h  Spec. No.  ^1/L  126 106 111 115 95 120 90  28 . 6lb 66b 67 73 78 8l  On the average  .Fe r i c h  constituent  118 95 93 110 86 111 86 "  L= ±  load.  L  2  constituent =  50g  2  1.07 ' 1.12 1.19 1.05 1.10 1.08 1.05  143 172 ~v 201 140  -  ^l/L  2  122 143  1.17 1.20  169 124  1.19  -  the 10 g' l o a d gave 9$ h i g h e r r e a d i n g s f o r the  r i c h c o n s t i t u e n t and 17$ h i g h e r f o r the i r o n - r i c h :  IUg  -  i.13  -  copper-  c o n s t i t u e n t t h a n the 50 g  - 57 -  APPENDIX I I  Processing and Tensile Data Spec, Fe Powder Nal .1 Meahr.'Size  12 -80 +150 it 13 M 16 17 it 18 19 -100 +150 23 -200 +270 24 " 25 " 26 " 27 " 28 " 29 31 " 36 37 11 38 " 39 " 40 4l 42 43 " 44 " 45 " 46 " 47 •• 48 -100 +150 49 50 II  Compact. Sintered Pressure Density psi.  30,000 11  20,000 11 11  30,000 11 tt 11 11 it 11 11 11  1150 ' 10 75.0 it 11 77.0 11 11 68.6 11 ti 68.8 . it 11 69.4 tt it 72.8 it 77-8 200 tt tt 77-4 11 11 79-5 11 77-4 10 it 11 78.8 11 tt 77-7 11 60 If • 11 78.5 11 63.3 10 11 . tt .62.6 it tt 59-8 it II 69.8 tt II 70.7 11 tt 74.7 II 77-3 1260 It tt 77-4 II It 77-2 It 78.0 1100 It tl 78.3 II It : 78.6 tt 76.0 1150 tt tl 76.0 II II 75-8 ' !  nil it tt  20,000 ti it  30,000 it it tt 11 11. tt tl tl  Infiltration . Temp. Time °C min.  Infilt. Density  Tensile Propert ies xS UTS E p s i . '• psi.. 1o  18,900 21,000 16,200 16,800 17,700 21,200 98.15 54,500 54,600 98.48 54,700 97.89. 17,000 98.15 20,900 97-99 20,000 ,33,500 '*98.42 28,200 97.96 23,200 97.67 . 25,100 23,200 97-32 . 23,000 23,800 97-88 20,900 32,300 97.94 • 51,800 36,700 98.27 97-64 18,600 96.84 18,800 95-79 18,400 97.58 21,900 96.69 19,900 96.91 20,900  32,000 33,400 32,800 40,300 40,800 45,600 . 59,700 67,200 62,700 38,400 38,300 39,100 46,800 45,500. 37,300 28,500 43,200 32,400 4o,ooo 35,500 46,800 51,800 52,400 40,800 37,000 35,700 45,400 42,200 41,300  continued  8.0 10.0 8.5 25.0 28.0 25.0 4-5 3-5 3-5 9.6 7-0 9.4 7-0 7-0 7-5 3-0 5-0 3-5 8.0 8.0 3.0 0 8.0 16.0 13.5 9-5 16.0 23.0 TOAjt 2A0  - 58 Appendix I I ( C o n t i n u e d )  Spec. No.  51 52  53 55 57  59 6lb  Fe Powder Mesh S i z e  -150 +290 11  11  -270 +325. -325. -20011 +275  62c  11  66b  11  67 69 73  75 77 78 79 85  86  89 90  •'  11 11  -100 +150, 1!  Compact. Pressure psi.  Sintered Density  30,000  77 »3 76.6 77-3 •' 75-4 74.0 75-0 60.2 58.2 71.4 77-375-8 74.0 73-7 74.2 77-6 76.9 76.2 76.2 79.8 77.2 76.9  11 11 11 11 11  nil ii  20,000 30,000 it 11 11 11  -200 +270  11  11  11  n  it  -270 +325 -325 -200 +270 11  11 11 11  ^Specimens b r o k e o u t s i d e gauge mark  Infiltration . Infilt. Temp. Time Density °C °c • t 1150 11  11  11  11  11  11  11  11  11  420  ti  .  10  120  n  11  it  11  11  11  ti  11  ti  tt  i t 11  1370  11 11  10  It  11  It  11  1150  120  11 tt 11  300 it  '97.76 96.97 97.65 97-52 97.47 98.I6 98.36 98.25 98.05 97.82 97-73 ' 98.21 98.02 98.58 97.56 97-79 97-74 97-90 99-20 98.50 98.10  Tensile Properties UTS YS E psi. psi. fo  20,500 19,000 23,200 23,60*0 27,500 56,100 35,200 30,300 45,600 42,000 36,000 36,400 35,800 39,500 46,800 53,200 62,300 4i,ioo 40,200 55,300 57,700  38,000 38,000 41,300 46,600 37,400 66,900 42,200 41,300 50,700 . 52,800 48,400 53,300 47,600 45,400 54,500 60,800 62,300 klgoo 4o,4oo 64,700 57,700  .18.5* 16.5 17.5 12.0*  5-0  1.0  4.0  1.0* 2.0 5.0  4.0 .7,5 4.5 2.0 2.0 2.0 0  075 0-5  4.0 0  - 59 -  APPENDIX I I I  M e t a l l o g r a p h i c Measurements  Spec. No.  :  *  19 25 28 31 36 39 4o 44 46 • 50 53 55 57 59 6lb 66b 67 73 78 85 : 86 89 .  Vol.70 copper  20.7 19.6 19.6 21.3 39-9 27.7 (25.4) 19.7 23.5 22.3 23.2 24.0  21.5  24.0  37,7 26.0 19,9 • 24.5 20.9. 25.3 21-5 25.4  Diameter o f Iron part.  A 91.-6 53-5 48.7 50.2 43.2 47.9 43.8 51-3 46.7 81.0 58.8 37-9 21.7 52.9 44.7 46.3 52.6 92.7 • 50.1 40.9  34.3 53.9  Mean F r e e Path  A 24.0  13-0 11.8 13.7 28.7 18.5 14.9 12.6 14.3 23.2 17-7 11-9 6.0 16.8 2.7-3 16.2 13-1 30.2 13.2 13-8 ' 9-3 18.3  Inter particle spacing,/i/  115.6 - 66.5 60.5 63.9 771.9  66.4 58.7 63.9 61.0 104.2  76-5 49.8 27-7 69-7 72.0 '62 ;5 ' 65.7 122.5 63.3 54.7 43-7 72.2  t e s t s w i t h 10 1 l l o a d , w h i l e the r e s t w i t h 50 g l o a d  Microhardness, VHN . Cu r i c h Fe r i c h . phase phase  114 117 118 117 106* 105* -  118 204  122 137 145* 148* 103  -  118 110 • 92* 106*  140  118 148* 143* 153* 154* 206  ill*  117* ill  143  118 169 124 165 197* 229* 203  •  95 93 110 86  .  i l l  105* 125* 112  - 60 -  VII.BIBLIOGRAPHY  . 1.  E l l i o t , J.E., M e t a l l u r g i a 5 2 ,  ( 1 9 5 5 ) 226-234.  2 . - "Metals Handbook", 1948 e d i t i o n , A.S.M. 3.  Whalen, T.ff., Humenik, M.,  4.  K i n g e r y , W.D.,  5.  Inman, M.,  6.  T a y l o r , J.W.,  Progress i n Nucl. E m . S e r i e s  7.  S w a l i n , R.A.,  "Thermodynamics o f S o l i d s " ( 1 9 6 2 ) , John W i l e y and  New  P r o c . l 8 t h Ann. Powder Met.  J . A p p l . Phys. 3 0 , 3 ( 1 9 5 9 )  Met. Review 8 ,  30 ( 1 9 6 3 )  Conf. 18 ( 1 9 6 2 )  301.  120. 5,  2 (1959)  398Sons,  York, 2 0 5 -  8.  B a r r e t t , C.S.,  9.  E d e l s o n , B.I.,.. Baldwin, W.M.,  " S t r u c t u r e of Metals.'' ( 1 9 5 2 ) , M c G r a w - H i l l , New Trans'. . Quart. A.S.M. 55 1  Krock, R.H.,  11.  Gregory, E., Grant, N|cf., T r a n s . A.I.M.E. February ( 1 9 5 4 )  12.  P i n e s , B.Y.,  13.  T e o d o r o v i c h , O.K.,  Shepard, L.A.,  T r a n s . A.I.M.E. 22J_ ( 1 9 6 3 )  1.0.,  Radomyselsky,  230-250.  247. 2076.  Poroskpvaya M e t a l l u r g i a ,  63.  14.  Kimura., T., P l a n s e e b e r i c h t e f u r Pulvermet J_, 2 ( 1 9 5 9 )  15.  G o e t z e l , C.G.,  P r o d u c t Eng. 18  16.  Heheman, R.F.,  Luhan, V.iJ., T r o i a n o , A.R.,  17.  K o p e c k i , E.S.,  I r o n Age  18.  Kelley, F.C,  19.  N o r t h c o t t , L., Loadbeater, C.'«J., S p e c i a l Report No.  I r o n Age  350.  1127-  S u k h i n i n , N.I., J . Tech. Phys. U.S.S.R. 26 ( 1 9 5 6 )  U.S.S.R. 4 ( 1 9 6 1 )  (1947)  York,  (1962)  10.  (1947)  15J_ ( 1 9 4 6 ) 15_7  (1946)  50.  115. T r a n s . A.S.M. 4_9_ ( 1 9 5 7 ) 4 0 9 -  50. 57. 3 8 , I r o n and S t e e l Ins.  142.  20.  Smith, C S .  21.  Renhhack, 'E.H.,Pioc. 1 7 t h Annual Powder Met. Conf.  22. 23.  85.  Palmer, E.W.,  i  J . M e t a l s 1 8 8 12  (l950)  i486. (1961)  12,  T e o d o r o v i c h , O.K., F r a n t z e v i c h , I.N., Porosk, Met. UpS.S.R. 6 ( 1 9 6 1 ) . G o e t z e l , C.G., " T r e a t i s e on Powder M e t a l l u r g y " 2 ( 1 9 5 0 ) I n t e r s c i e n c e .  - 61 -  2{j[.  Schwartzkopf,  25.  Gurland, J . ,  26.  Hames, F . A . , Gertsman,  27.  Frant^evich,  P.,  Met. P r o g r e s s  Norton, J . T . ,  J.  S.L.,  57 (1950) 64.  Metals4 Int.  I . N . , Teodorovich,  (1952,) 1051.  Report,  D e p t . o f M i n e s , PMI 6l~24  (1961).  O . K . , M e t a l l o b e d . i . O b r . Met. U . S . S . R . , 9_  (1958) 20. 28.  Underwood, E . E . , M e t . E n g . Q u a r t .  29.  Fullman, R . L . , T r a n s . A . I . M . E . . l g l  30.  Semlak, K . A . , R h i n e s ,  31.  Kuzmik, J . F . ,  32.  Price,  33-  Bredzs,  1 3,4 (1961).' (1953) 447-  F . N . , Trans. A . I . M . E .  Mazz'a, E . N . , J .  G . H . , Smithells,  Metals,  212 (1958) 325-  October  (1950) 1218.  C . J . , W i l l i a m s , S . l f . , 'J.. I n s t ,  N . , S c h w a r t z b a r t , H . , S u p p l . Welding J .  August  62 (1938) 239.  o f Met.  (1959). ji''! -'  34.  Lenel, F . V . , Ansell,  35-  B u c k l e r , H . , P r o c . Powder Met. C o n f . , New York  G . S . , P r o c . Powder. M e t . C o n f . , Ne¥ Y o r |  (i960) 221.  (i960) 267.  

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