A mechanism-based multisurface plasticity model for hexagonal close-packed materials with detailed validation and assessment

Abstract

We present a multi-surface model (MSM) of plasticity to simulate the anisotropic and asymmetric yield responses often observed in hexagonal close-packed (HCP) materials such as magnesium and its alloys. Motivated by the salient outcomes from high-resolution polycrystal plasticity simulations and experimental insights on magnesium alloys, we propose a three-surface representation incorporating two separate anisotropic, symmetric yield surfaces for the soft (basal) and hard (non-basal) glide, and an anisotropic, asymmetric yield surface for extension twinning. This reduced representation of the high-resolution crystal plasticity offers computational attractiveness to analyze large-scale engineering simulations while maintaining key micromechanical details of soft versus hard glide. The model is calibrated to a particular three-dimensional dataset for polycrystal magnesium alloy and is validated against a range of crystal plasticity results for different loading conditions. The capability of the model is then assessed for complex boundary-value problems at the macroscale (round notched bars) and at the microscale (void growth and coalescence). The validation and assessment demonstrate the ability of the proposed MSM to capture finer details of deformation such as identifying regions where soft and hard glide may occur around the void or in other heterogeneous loading states.