Investigation the micromechanisms of strain localization formation in AZ31 Mg alloy: A mesoscale 3D full-field crystal plasticity computational homogenization study

Abstract

Wrought magnesium alloys exhibit strong basal texture after extrusion or rolling process. In this study, a numerically improved crystal plasticity finite element model in conjunction with computational homogenization has been used to investigate the micromechanism of strain localization in AZ31 Mg alloy under uniaxial tension along rolling direction (RD), uniaxial compressin along normal direction (ND) and biaxial tension in RD-TD plane. To this aim, the effect of texture and especially off-basal grains distribution on strain localization is elaborated in detail. Three realistic representative volume elements (RVE) of microstructure with 34, 60 and 58 grains and ≈578, ≈546and ≈1103 elements per grain have been synthetically constructed and analyzed to examine the effect of basal and off-basal grains distribution on the deformation patterns. Strongest strain localization was found in RVE. 1 where off-basal grains were arranged in a banded form. RVE. 2 with differing spatial position of off-basal grains showed weaker, yet discernible localized band. RVE. 3 with a nearly random distribution of off-basal grains depicted no clear side-by-side localized band. It was found that basal slip is the main contributor of compound strain localization regions. Moreover, high stresses inside the localized band can enforce well-oriented grains for non-basal slip located between off-basal grains to deform cooperatively. Upon the formation of localized bands, the remaining part of the RD-TD faces experienced insignificant deformation and clear deformation partitioning occurred. Regarding RD-ND faces, two distinct microscale localized zones have been observed. Basal and prismatic slip was the former of localized zones on the RD-ND faces.