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对AZ91镁合金在均质化热处理、热挤压和时效处理中的组织演化规律进行研究。研究结果表明,在铸态组织中存在离异共晶和固态析出两种β-Mg17Al12相。在最佳的均质化处理(380℃,15h)过程中,β-Mg17Al12相大部分溶解到α-Mg基体中,并且晶粒细小。在热挤压过程中发生动态再结晶以及由此产生的晶粒细化。而时效处理之后则出现平行于挤压方向的带状β-Mg17Al12相析出,这应该是由于在挤压过程中把原始铸造偏析挤扁拉长而造成的。另外,根据实验结果,详细地讨论了均质化和时效处理的温度、保温时间以及挤压工艺参数对AZ91镁合金的组织变化产生的影响。
The microstructure evolution of AZ91 magnesium alloy during homogenization heat treatment, hot extrusion and aging treatment was studied. The results show that there exist two types of β-Mg17Al12 phases in the as-cast microstructure, such as divorced eutectic and solid state precipitation. During the best homogenization (380 ℃, 15h), the β-Mg17Al12 phase mostly dissolves into the α-Mg matrix, and the grains are fine. Dynamic recrystallization occurs during hot extrusion and the resulting grain refinement. After the aging treatment, the strip-shaped β-Mg17Al12 phase precipitates parallel to the extrusion direction, which should be due to squeezing and elongating the original casting segregation during the extrusion process. In addition, according to the experimental results, the effects of homogenization and aging treatment temperature, holding time and extrusion process parameters on the microstructure of AZ91 magnesium alloy were discussed in detail.