铸轧AZ31镁合金的高温拉伸性能

High temperature tensile behaviors of twin-roll cast AZ31 Mg alloy

研究了铸轧AZ31镁合金的高温拉伸性能和变形机制.在300～450℃条件下,分别以恒定拉伸速率10^(-3)s^(-1)和10^(-2) s^(-1)进行拉伸至失效试验,在真实应变率为2×10^(-4)～2×10^(-2) s^(-1)的范围内进行变应变率拉伸试验.当拉伸速率为10^(-2)s^(-1)时,试样在400℃和450℃的延伸率均超过100%;当拉伸速率为10^(-3) s^(-1)时,试样在400℃和450℃的延伸率均超过200%,该条件下的应力指数n≈3,蠕变激活能Q=148.77 kJ·mol^(-1),变形机制为溶质牵制位错蠕变和晶界滑移的协调机制.通过光学金相显微镜和扫描电子显微镜观察显示试样断口处存在由于发生动态再结晶和晶粒长大而形成的粗大晶粒,断裂形式为空洞长大并连接导致的韧性断裂.

This paper reports the high temperature tensile deformation behaviors and mechanisms of twin-roll cast AZ31 magnesium alloy. At constant temperatures ranging from 300 ℃ to 450 ℃, the elongation-to-failure test was conducted under constant tensile strain rates of 10^-3 s-1 and 10^-2 s^-1, and the strain-rate-change tensile test was performed under strain rates from 2×10^-4 s^-1 to 2×10^-2 s^-1. The elongations of specimens at 400 ℃ and 450 ℃ are both higher than 100% when the tensile rate is 10^-2 s^-1. But when the tensile rate is 10^-3 s^-1,the elongation values at 400 ℃ and 450 ℃ are both higher than 200%, the stress exponent n is about 3, the creep activation energy Q is 148.77 kJ.mo1^-1, and the deformation mechanism is a collaborative mechanism of grain boundary sliding and solute-drag dislocation creep. Optical microscopy and scanning electron microscopy observations show that coarse grains develop at the failure ends due to dynamic recrystallization and grain growth, and the fracture is of a ductile pattern caused by cavity growth and interlinkage.