High Temperature Deformation Mechanism And Texture Of Twin-roll Casting AZ31 Magnesium Alloy

This paper investigated the dynamic recrystallization behavior, deformation mechanism, and microstructures evolution of twin-roll-cast AZ31 magnesium alloy sheet with fine grains. It focused on dual- mechanism constitutive model for a large range of strain rates from 5×10-5 to 10-1 s-1, high temperature texture evolution, and activation of basal ? ?0 0 0 2 11 2 0, prismatic ?10 1 0? 112 0 and pyramidal ?112 2? 1 1 23 slip systems of AZ31 magnesium alloy under different strain rates.Under high temperatures(350, 400, and 450 ℃) and strain rates of 10-1, 10-2, and 10-3 s-1, fixed-strain texts at the strain of 0.45 were conducted. Strain- hardening curves, microstructures, and grain-size difference between grip and gauge of specimen were investigated to study dynamic recrystallization under different deformation conditions. The results show that decreasing strain rate and increasing temperature inhibit occurrence of dynamic recrystallization. Specimens conducted tensile tests at 450 ℃ and low strain rates has very low volume fraction of dynamic-recrystallized grains.Under high temperatures(350, 400, and 450 ℃) and strain rates of 10-1, 10-2, and 10-3 s-1, elongation-to-failure texts were conducted. At the same temperatures, strain rate change(Strain Rate C hange, SRC) tensile tests were conducted to calculate stress exponent and activation energy. It shows that grain boundary sliding(GBS) is the dominant deformation mechanism at 450 ℃ and 10-3 s-1, and dislocation climb creep(DCC) is the dominant deformation mechanism under other deformation conditions. The high temperature deformation mechanism is a competitive mechanism of GBS and DCC, and an estabilished dual- mechanism constitutive model fit the experiment data successfully.Under constant temperature of 450 °C and strain rates of 10-3, 5×10-3 and 10-2 s-1, fixed-strain tests at the strain of 0.45 were conducted. Texture characteristics were investigated using X-Ray diffraction(XRD), and activation of slip systems was investigated by the Schmidt factor of force in different slip directions. The results show that the initial basal textures are significantly weaken after tensile tests; specimens under different tensile rates form the same high- intensity texture components, but different low- intensity texture components, and each texture components facilate to dislocation slip.