Deformation behavior and tensile properties of an austenitic Fe-24Mn-4Cr-0.5C high-manganese steel: Effect of grain size

Deformation behavior and tensile properties of an austenitic Fe-24Mn-4Cr-0.5C high-manganese steel with different grain sizes were discussed in this study. Effective grain size including annealing twins and stacking fault energy increased with increasing annealing temperature from 800 °C to 1200 °C. Room-temperature tensile test results indicated that the yield and tensile strengths increased, but the total elongation decreased with decreasing the effective grain size. According to electron back-scattered diffraction and transmission electron microscopy analyses, the deformed microstructure of all the specimens having stacking fault energy between 24.0 mJ/m² and 31.6 mJ/m² showed deformation twinning. However, the formation of the deformation twinning was suppressed with decreasing the grain size, resulting in different work hardening behaviors. Experimental and calculated twinning stress increased with decreasing the grain size because dislocation activity and the movement of partial dislocations required for form the deformation twinning were further inhibited by interaction of relatively high dislocation density in specimens with finer grain size.