Effect of temperature and interstitial composition on the yielding of niobium single crystals
department or school: Applied Science, Faculty of
department or school: Materials Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Harding, Hugh James
issued: 2011-11-29T20:51:58Z
issued: 1961
related degree: Master of Applied Science - MASc
degree grantor: University of British Columbia
description: An investigation of the effect of temperature and interstitial composition on the yielding characteristics of high purity niobium single crystals has been carried out. Single crystals of [110] axial orientation were purified and grown using an electron beam, floating-zone, zone-refiner. Tensile specimens prepared from the single crystals were tested in tension at temperatures from +25° to -197°C. at a strain rate of 0.057 per minute. The variation of yield stress with testing temperature was found to be discontinuous and consisted of two curves which intersected at approximately -100°C. The tensile results can be correlated to both Fisher's interpretation of the Cottrell-Bilby theory of yielding and to the theory of Zener and Holloman, which involves a thermally activated process. The effect of additions of hydrogen, oxygen and nitrogen to niobium single crystals over the temperature range +25° to -197°C was to increase the yield stress. The unusual temperature dependence of yield stress has been explained in two possible ways: 1. Ordering or superlattice formation at the temperature at which the anomalous behaviour occurs. 2. The preferential release of screw dislocations at stress levels lower than that required for edge dislocations. The result is a decrease in the temperature dependence of yield stress at the temperature when edge dislocations begin to take part in yielding.
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/39364
note: EFFECT OF TEMPERATURE AND INTERSTITIAL COMPOSITION ON THE YIELDING OF NIOBIUM SINGLE CRYSTALS HUGH JAMES HARDING A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE IN THE DEPARTMENT OF MINING AND METALLURGY We accept t h i s t h e s i s as conforming to the standard required from candidates f o r the degree of MASTER OF APPLIED SCIENCE Members of the Department of Mining and Metallurgy THE UNIVERSITY OF BRITISH COLUMBIA September 1961 In presenting t h i s t h e s i s 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 U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. Department of Mining and Metallurgy, The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date August 28th, 1961 ABSTRACT An i n v e s t i g a t i o n of the e f f e c t of temperature and i n t e r s t i t i a l composition on the y i e l d i n g c h a r a c t e r i s t i c s of high p u r i t y niobium sin g l e c r y s t a l s has been c a r r i e d out. Single c r y s t a l s of [liojj a x i a l o r i e n t a t i o n were p u r i f i e d and grown using an e l e c t r o n beam, floating-zone,zone-refiner. T e n s i l e specimens prepared from the single c r y s t a l s were tested i n tension at temperatures from +25° to -197°C. at a s t r a i n rate of 0.057 per minute. The v a r i a t i o n of y i e l d stress with t e s t i n g temperature was found to be discontinuous and consisted of two curves which in t e r …
has type: Thesis/Dissertation
is shown at: 10.14288/1.0105852
language: eng
degree discipline: Metals and Materials Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/39364