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

The deformation-induced transformation characteristics and texture evolution of alpha '-martensite during cold rolling together with the tensile properties of two specially prepared initial microstructures (bimodal elongated gamma grains and fine equiaxed gamma 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 gamma 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} < 110 >(alpha) from the Copper-type gamma texture and {332}< 113 >(alpha) from the Brass-type gamma texture, whereas {001}< 110 >(alpha) 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 gamma grains preferentially transformed to martensite rather than gamma grains with Brass orientation.

Automated summary

The thermally induced martensite can be effectively restrained by refining grains or introducing crystal defects, providing a nearly full austenite phase for the subsequent TRIP process. Fine-grained samples exhibit better plasticity and higher strength, while bimodal elongated-grained samples demonstrate the highest strength and sufficient plasticity due to the delay in martensitic transformation.