Anisotropic deformation mechanisms of AZ31B mg alloy under torsional and torsion–axial coupled loadings

This study systematically investigates the anisotropic deformation mechanisms of AZ31B magnesium alloy under torsional and torsion–axial coupled loadings, aiming to clarify the mechanisms of shear-dominated multiaxial deformation. Through integrated experiments and numerical simulations, we examine torsional characteristics and torsion-tension/compression coupling effects in AZ31 Mg alloy specimens with varied initial textures. Experiments included free-end torsion and coupled torsion-tension tests, while simulations employed an elastic-viscoplastic self-consistent (EVPSC) model incorporating twinning-detwinning (TDT) mechanisms and a torsion-specific finite element (TFE) methodology. The model accurately reproduces: (1) Highly anisotropic, texture-dependent torsional responses; (2) Complex coupling behaviors under combined loading; (3) Constitutive model-sensitive Swift effects. Mechanistic insights were enhanced by analyzing stress/strain distributions, twin volume fraction (TVF) evolution, deformation mechanism activation, and texture development. These findings bridge the knowledge gap between homogeneous and inhomogeneous deformation in Mg alloys and offer guidance for tailoring twinning activity to enhance formability under complex loading. • Torsional and torsion-tension/compression of Mg alloy was systematically studied. • TFE-EVPSC-TDT model captured anisotropic torsional response and Swift effect. • Coupled torsion-tension and torsion-compression exhibit opposite effects on twin. • Axial stress regulates the gradient twinned structure formed under torsion.