回位-結晶塑性Cosseratモデルに基づくMg基LPSO相のキンク帯形成に関する数値解析手法の検討

抄録

Kink deformation, which occurs in the long period stacking ordered (LPSO) structure phase of Mg-TM-RE alloys, is considered to affect the excellent mechanical properties of this alloy. Although the mechanism of kink band formation was explained by segregation and rearrangement of dislocation, it is recently attempted to express the kinking process from the viewpoint of a rotational line defect called disclination. We developed a new model of Cosserat continuum consistent with the framework of the crystal plasticity by describing the microscopic plastic rotation as a quantity of each slip system and conducted meshfree analysis for a plate of a LPSO single crystal. However, a meshfree method imposing boundary conditions using Lagrange multipliers is not exactly consistent with the principle of virtual work. In this study, finite element method (FEM) using penalty parameters for boundary conditions is adopted to the dislocation-based crystal plasticity Cosserat model considering disclination density and it is shown that FEM can also reproduce the kink formation by use of disclination quadrupole structure and array structure of GN dislocation formed in the vicinity of the kink band as well as meshfree method. Furthermore, a size effect owing to the intrinsic length scale of Cosserat model is properly expressed under a boundary condition on rotational degree of freedom.