UBC Theses and Dissertations
Investigating the effect of Mn content on the microstructure and mechanical properties of high manganese steel Gautam, Sadhak
Hadfield steels, also known as high manganese (Mn) steels (HMS), are often used to fabricate components for crushing equipment, because of HMS’s high wear and impact resistance arising from the alloy’s high hardness and toughness. The composition of Hadfield steels has a significant effect on mechanical properties of the alloys. In this research, the effect of varying Mn (12-23 wt. %) on the ternary Fe-Mn-C system, microstructure and mechanical properties of HMS alloys was studied. Liquidus projection of ternary Fe-Mn-C diagram revealed the decrease in liquidus temperature with an increase in Mn from 12 to 23 wt. %. Microstructure analysis revealed that an alloy with 12 wt. % Mn had intermittent carbides at the grain boundaries. For alloys with 18 and 23 wt.% Mn, discontinuous carbides had a lamellar structure and formed at the grain boundaries and intergranular regions. The average grain size increased with an increase in the Mn concentration in the alloys. Energy dispersive spectroscopy (EDS) map, line, and point/area scans revealed the accumulation of chromium (Cr) and Mn on the carbide sites in all the alloys. (Fe,Cr)₂₃C₆ intermetallic compound was present in all the alloys, with a slight variation of Cr and Fe in localized areas. The Fe₁․₈Mn₁․₂C was present in alloys with 12 and 18 wt. % Mn, whereas Fe₁․₁Mn₃․₉C₂ was present in an alloy with 23 wt. % Mn. Mechanical testing (impact and tensile) revealed that the Charpy-impact values reached the highest value at 23 wt. % Mn addition and were lower for other alloy compositions. With an increase in Mn content in the alloys, the yield strength increased, whereas the ultimate tensile strength and elongation decreased. The hardness increased with an increase in Mn wt. % in the alloys. Finally, the weight loss of material during pseudo-wear testing decreased with an increase of Mn from 12 to 18 wt.% then remained constant for an alloy with 23 wt. % Mn.
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