The asymmetric pre-yielding behaviour during tension and compression for a rolled AZ31 Mg alloy

Tensile and compressive pre-yield mechanical behavior of a rolled AZ31 Mg alloy sheet was studied by cyclic loading–unloading tests along rolling direction (RD) and transverse direction (TD). The results show that the mechanical response of pre-yielding is not linear elasticity. Microplasticity with irreversible strain and energetic dissipation is observed during tension. While anelasticity with reversible strain and dissipative energy is detected during compression. A stress dependent varied elastic modulus model was built by introducing a stress factor to capture the asymmetric behavior. Three model parameters are tensile yield strength, initial elastic modulus and critical modulus at tensile yield point. Consequently, this model is verified by comparison with the experimental observations. The anelastic and micro-plastic deformation are ascribed to the glide of mobile dislocations. The asymmetric behavior of tension and compression is clarified by the nucleation mechanism of {10–12} twinning.