Abstract:

Texture and microstructure evolution in two kinds of the twinning induced plasticity (TWIP) steels (Fe-Mn-Si-Al and Fe-Mn-C) with diverse stacking fault energies during tensile testing were investigated by interrupted testing. The strain-hardening rate curves of the two steels were quite similar, but the texture characterization curves (maximum of pole density measured by X-ray diffraction) were varied. According to the curvature of max pole density curves, the evolution of the texture and the microstructure can be divided into three stages: low strain stage, medium stage and high stage. In low strain stage the difference of the microstructure came from the intensity of dislocation, which was much smaller in Fe-Mn-Si-Al. The main difference of the microstructure in medium and high strain stages originated from the numbers of activated twin systems. There were more than one twin systems activated in Fe-Mn-C, while only a single twin system activated in Fe-Mn-Si-Al. Texture showed various differences in the whole tensile process because it was affected by their micromechanism, such as concentration of the dislocation and the activation of twin systems. Texture in low strain stage was connected with annealing twin; the evolution ofthe texture was mainly induced by deformation twin generation. More than one activated twin systems in medium and high stages may counteract each other in the view of concentration of the grain orientations.

Key words: Work hardening rate, Texture, TWIP steel, Stacking fault energy