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SCNIによるメッシュフリー解析

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. However, a meshfree method using background integration cannot ensure balance at each node. Therefore, extrapolation from sampling points to nodes is needed for the calculation of crystal defects such as geometrically necessary (GN) dislocation density. In this study, meshfree analyses with stabilized conforming nodal integration (SCNI) based on the dislocation-based crystal plasticity Cosserat model considering disclination density is conducted and it is shown that this model can reproduce the kink formation by use of disclination quadrupole structure and array structure of GN dislocation formed in the vicinity of the kink band. Furthermore, a size effect owing to the intrinsic length scale of Cosserat model is properly expressed by imposing boundary condition on rotational degree of freedom.