科研之友
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摘要
Twinning induced softening (i.e. stress drop) is a non-negligible deformation characteristic related to twin nucleation, propagation and growth (TNPG) of twinning-induced plasticity (TWIP) steel single crystals. However, the mesoscale physical-based TNPG models considering the softening effect are applied at the crystal level and cannot provide insight into the dislocation activity within grain or at grain boundary. In this paper, a dislocation-density-based constitutive model was proposed to describe the evolution of the TNPG process based on dislocation theory integrating the twin-energy pathway. Then the model was employed to reflect the deformation mechanisms of TWIP steel single crystal in plastic deformation processes. The results show the twinning induced softening was caused by different critical shear stress for twinning (CSST) nucleation and growth, and the twin nucleation and growth were conducted by partial dislocation emission from an inner source and a surface source, respectively. The CSST for nucleation was larger than that for growth since no additional faulting energy had been introduced in twin growth. Furthermore, different leading partial dislocations were obtained under tension and compression even with the same orientation, which resulted in the tension-compression asymmetry in twinning nucleation.
