Influences of initial microstructures on martensitic transformation and textures during cold rolling and tensile mechanical properties in high manganese TRIP steel

Abstract The deformation-induced transformation characteristics and texture evolution of α′-martensite during cold rolling together with the tensile properties of two specially prepared initial microstructures (bimodal elongated γ grains and fine equiaxed γ grains) were investigated in high manganese TRIP steels. The results showed that the thermally induced martensite was restrained effectively by refining grains or introducing crystal defects like dislocations, which provided a nearly full austenite phase for the subsequent TRIP process. Compared with the solution-treated sample containing coarse equiaxed γ grains, the fine-grained sample revealed a better plasticity and a higher strength due to grain refinement and progressive TRIP process. The bimodal elongated-grained sample exhibited the highest strength and sufficient plasticity because the dislocation strengthening exceeded the fine-grain strengthening and martensitic transformation was delayed. The transformation textures of two kinds of samples differed in that the fine-grained sample demonstrated typical {113} α from the Copper-type γ texture and {332} α from the Brass-type γ texture, whereas {001} α texture occurred in the bimodal elongated-grained sample in addition to the above two components. In the early stage of TRIP, there was an obvious orientation dependence, and the {100}- and Copper-oriented γ grains preferentially transformed to martensite rather than γ grains with Brass orientation.