Work hardening and softening behavior of pure Mg influenced by Zn addition investigated via in-situ neutron diffraction

Abstract

The work hardening and softening behavior of pure Mg influenced by Zn addition were studied through the neutron diffraction at STRESS-SPEC under in-situ tensile deformation. The measurement of the line broadening evolution during in-situ tension was used to study the variation of dislocation density in pure Mg and Mg–5Zn alloy, which revealed the effect of dislocation on work hardening behavior. Meanwhile, the tensile stress reduction (△Pi(i=1,2,3)) due to the softening effect at different in-situ tensile deformation stages were calculated to analyze the effect of Zn addition on softening behavior. The results show that the work hardening rate of pure Mg is larger than that of Mg–5Zn alloy in the early stage of deformation because of the stronger effect of grain size on the work hardening behavior. But the work hardening rate of Mg–5Zn alloy is higher than that of pure Mg in the later stage of deformaiton, which is attributed to the stronger effect of precipitates on work hardening behavior. Moreover, △P1 of pure Mg is larger than that of Mg–5Zn alloy, which was explained by the large grain size of pure Mg results in higher stored energy during the early deformation stage, and providing a greater driving force for the softening behavior. However, with the increase of tensile strain, the increase significantly of the stored energy in Mg–5Zn alloy due to the dislocations migration hindered by precipitates during the tensile deformation, leading to a higher driving force for softening behavior in the later deformation stage. Thus, △P3 of Mg–5Zn alloy is larger than that of pure Mg.