[SY-C2] Symposium C-2

[SY-C2] Dynamic recrystallization model for Mg/LPSO alloys coupling phase-field model and dislocation-based crystal plasticity model

^○Sho KUJIRAI¹, Kazuyuki SHIZAWA² (1.Grad. School of Science and Technology, Keio Univ., Japan, 2.Dept. of Mechanical Engineering, Keio Univ., Japan)

Magnesium alloy with LPSO (Long-Period Stacking Ordered Structure) phase has been developed and attracted much attention for a next-generation structural material because of its outstanding mechanical properties, i.e., high yield strength, light specific weight and flame retardance. This alloy is mainly composed of α-Mg and LPSO phases. The strengthening mechanism of this alloy is attributed to a kink band formulation in LPSO phase and a grain refinement of α-Mg phase in the vicinity of LPSO phase. The deformation kink, which is one of plastic buckling in laminated materials, is formed by dislocation glide in basal slip systems. The grain refinement of α-Mg phase occurs through the dynamic recrystallization in a warm plastic work. The dynamic recrystallization is a self-organization phenomenon that recrystallized nuclei grow in the deformation process of α-Mg phase. Mechanical properties of structural metals are mainly determined by microstructures generated in the deformation process. Our research group recently developed a dynamic recrystallization model for FCC crystals by coupling the multi-phase-field (MPF) model with the dislocation-based crystal plasticity model as a strain gradient theory. In this report, we extend the above multiphysics model to that for HCP crystals so that we can predict the strengthening behavior of Mg/LPSO alloys. It is known that additional elements prevent the nucleus growth in α-Mg phase. Such effect is called the pinning effect and it is introduced into the present model. The grain boundary segregation of additional elements is also considered. We conduct multiphysics FE analyses for Mg/LPSO alloys and then reproduce the dynamic recrystallization along the deformation kink bands numerically. From the results obtained in this study, it is revealed that Mg/LPSO alloys are strengthened by the deformation kink in the LPSO phase, the grain refinement in the α-Mg phase and the interaction between those effects in the alloys.