Mg-12Gd-3Y-0.6Zr合金的二次挤压热变形行为

采用Gleeble-1500型热模拟机在变形温度为360~480℃、应变速率为0.01~10 s-1、真应变为0~0.7的条件下,研究Mg-12Gd-3Y-0.6Zr合金二次挤压过程的热变形行为,获得其热变形工艺参数,并分析热变形后的显微组织。结果表明:合金的峰值应力随应变速率的增大而提高,随应变温度的升高而降低;在变形温度、应变速率相同的情况下,一次热模拟的峰值应力均大于二次热模拟(450℃,10 s~(-1)除外);合金二次挤压过程的流变应力可以采用含Zener-Hollomon参数的双曲正弦函数形式来描述;由于二次热模拟试样中位错及晶界运动增强,使二次热模拟的激活能(Q)、应力指数(n)均小于一次热模拟的相应参数,导致二次挤压较一次挤压容易发生再结晶。

Hot deformation behavior of Mg-12Gd-3Y-0.6Zr alloy during secondary-extrusion process

The hot deformation behavior of Mg-12Gd-3Y-0.6Zr alloy during secondary-extrusion process over the temperature of 360?480℃, the strain rate of 0.01?10 s?1 and the true strain of 0?0.7 was studied by using Gleeble-1500 hot simulator machine. The process parameters of hot deformation were obtained, and microstructure after hot deformation was studied. The results show that the peak flow stress increases with increasing strain rate at constant temperature, and decreases with increasing deformation temperature at constant strain rate. Under the condition of the same deformation temperature and strain rate, thermal simulation of peak stress at one time is higher than that at two times (except 450℃/10s?1);the flow stress of Mg-12Gd-3Y-0.6Zr alloy during secondary-extrusion process can be represented by a Zener-Hollomon parameter in the hyperbolic Arrhenius-type equation. With the strengthening of dislocation and grain boundaries, both the value of activation energy (Q) and stress index (n) of secondary-hot simulation are smaller than those of single-hot simulation. Secondary-extrusion is easier than single-extrusion for dynamic recrystallization.