Influence of Cobalt Content on Austenite Stability and Strain-Induced Martensite Transformation of Nanocrystalline Fe-7Mn Alloy Fabricated by Spark Plasma Sintering

Recently, there has been a lot of research on the third generation of advanced high-strength steels as a solution to reduce CO2 emissions. The effect of Co addition on the austenitic stability of nanocrystalline Fe-7%Mn alloy was investigated by X-ray diffraction (XRD) analysis and microscopic observation. Fe-7%Mn-Co alloy samples with nano-sized crystal size were successfully prepared by spark plasma sintering. The austenite fraction in the sintered alloys was determined by the Averbach-Cohen model. The austenite fraction decreased with Co addition. The Burke-Matsumura-Tsuchida (BMT) model was also used to evaluate the austenite stability of the alloy as a function of Co addition. The austenitic stability decreased with increasing Co addition. This is because Co reduces the stacking fault energy (SFE), which reduces the austenite stabilizing effect and promotes martensitic transformation.