Flow softening, twinning and dynamic evolution of second phase particles in a rolled Mg–Y-Nd-Zr alloy under shear deformation mode

Abstract

Shear punch deformation was employed to study the shear deformation behavior as well as microstructural evolution of a Mg–Y-Nd-Zr alloy at a wide temperature range of 25–500 °C under different strain rates. The results showed that metastable β″andβ′ phases may dynamically precipitate during deformation. A flow softening behavior was also realized during shear deformation at different temperatures, which was explained by the evolution of second phase particles. The shear defamation mode promoted the contribution of extension twinning so that occurrence of twinning was traced even at temperature as high as 450 °C. Moreover, dynamic recrystallization took place at 450 and 500 °C. Electron backscattered diffraction analysis implied that progressive latticed rotation was operative as recrystallization mechanism, where remarkable texture changes were obtained. Shear flow stress could be successfully modelled by employing constitutive equations. The obtained activation energies as well as stress exponents suggested dislocation glide controlled by rare earth-diffusion as the rate-controlling mechanisms for temperature range of 25–400 °C, and grain boundary sliding controlled by lattice diffusion at 450–500 °C.

Keywords

• Shear deformation
• Mg-RE
• Second phase
• Recrystallization