Abstract

Microstructure and stress state closely interact in determining the strength and fracture resistance of ductile metals. While a fair understanding of the microstructure-stress interaction on strength, deformation stability and damage has been achieved for common engineering alloys, the same is not true for low symmetry hexagonal close packed (HCP) metals, e.g. magnesium (Mg). Mg, its alloys and composites are promising candidates as lightweight structural metals owing to their high power-to-weight ratio. However, the HCP structure of Mg exhibits complex deformation processes resulting in an intrinsic plastic anisotropy and tension-compression asymmetry at the single crystal scale, which is pervasive even in polycrystals. To that end, we probe the effect of textural variability and intrinsic plastic anisotropy on the macroscopic load-deformation characteristics of polycrystalline Mg aggregates using crystal plasticity finite element modeling (CPFEM). Our analysis underscores the need for a concerted multiscale computational effort for improved representation of the micromechanics in Mg at the structural length-scales. In this pursuit, we develop a multi-surface plasticity model (MSM) which embeds the key micromechanical features of plasticity and yet promises an enhanced computational efficacy. The MSM is assessed with the 3D datasets generated from a finer scale representation using CPFEM . The MSM is employed to study plastic flow in notched bars and micromechanics of void growth. In conjunction with the CPFEM , application of the MSM enables a multiscale perspective of deformation and damage evolution in Mg. Extended investigations along this path would guide development of lightweight and damage-tolerant Mg alloys.