Effect of Cold Rolling Deformation on Microstructure and Mechanical Properties of TWIP Steel

Microstructure and mechanical properties of TWIP（twinning induced plasticity） steel before and after cold rolling deformation were investigated by optical microscope, transmission electron microscope, X-ray diffraction and tensile test system. The results show that the TWIP steel always maintains a single austenite phase before and after cold rolling deformation. Dislocation accumulation and a small amount of deformation twins are formed in austenite grains after 30% cold rolling deformation. Meanwhile, the interactions between the twins and dislocations begin to happen. When the deformation increases to 50%, a large number of deformed twins are formed, and the interaction between twins and dislocations is significantly enhanced. When the deformation reaches 70%, the austenite grains are refined to nanoscale, and ultrafine sub-grains are formed. With the increase of cold rolling deformation, the yield strength and tensile strength of TWIP steel increase, and the elongation after fracture decreases.