Mg-Al-Zn-Nd稀土镁合金热压缩动态再结晶的研究

Study on recrystallization of Mg-Al-Zn-Nd magnesium alloy during hot-compression

采用Gleeble-1500D热模拟机对Mg-Al-Zn-Nd稀土镁合金的变形规律及动态再结晶行为进行研究。结果表明:合金的流变应力随应变速率的增大而增加,随温度的升高而降低;变形量对应力-应变关系的影响很小;变形过程中发生动态再结晶,随变形程度的增加,动态再结晶晶粒不断增多,材料呈现明显的软化趋势,流动应力下降。当动态再结晶过程完成以后,继续变形,材料又出现硬化行为;并且动态再结晶平均晶粒尺寸的自然对数与Zener-Hollomon参数的自然对数呈线性关系。根据实验分析,合金适宜的热加工条件为:变形温度400～450℃,应变速率0.1～5s-1。

The compression tests of Mg-Al-Zn-Nd alloy have been conducted on Gleeble-1500D hot simulation equipment. The results show that the flow stress becomes larger with increasing strain rate at the same temperature, and gets smaller with increasing deformation temperature at the same strain rate. The compressed amount does not apparently affect the relationship between the compressing stress and strain under the same deformation conditions. Dynamic recrystallization takes place during the deformation process. With deformation increasing, the amount of dynamic recrystallization grains increases, the materials take on obvious tendency of softening, and flow stress declines as well. After the completion of dynamic recrystallization process, the material is hardened again if deformation continues. The natural logarithm of dynamic recrystallization grains size is linear with the natural logarithm of Zener-Hollomon parameter. The temperature of 400-450℃ with strain rate of 0.1 ~5 s^-1 is suggested for hot deformation of this alloy.