Effects of grain size and temperature on mechanical properties of Fe–20Mn–0.7C TWIP steel

Abstract

Fe-20Mn-0.7C twinning-induced plasticity (TWIP) steel with the grain sizes in the range 1.7-10.2 μm was produced by cold rolling and annealing. The effects of grain sizes on the mechanical properties of the TWIP steel were studied by tensile test at room temperature (RT) and-180°C. The yield strength increased with decreasing grain size at RT and-180°C, and the corresponding Hall-Petch relationships were established at both temperatures and are as follows (i) σ 0.2 = 205 + 453 d-1/2 (at RT) and (ii) σ 0.2 = 317 + 755 d-1/2 (at-180°C). When the temperature decreased from RT to-180°C, the stacking fault energy decreased from 24to 17.9 mJ/m 2 , approximately 25%, and the deformation mode is transformed from deformation twins to martensite transformation.