往复挤压Mg-4Al-2Si镁合金的晶粒细化

来源期刊：中国有色金属学报2010年第4期

论文作者：宋佩维

文章页码：606 - 612

关键词：镁合金；Mg-4Al-2Si合金；往复挤压；动态再结晶；晶粒细化

Key words：Mg alloy; Mg-4Al-2Si alloy; reciprocating extrusion; dynamic recrystallization; grain refinement

摘    要：研究往复挤压Mg-4Al-2Si (AS42)合金的显微组织和晶粒细化机制。结果表明：挤压过程中发生受位错攀移控制的动态再结晶，随挤压道次的增加，合金的晶粒尺寸迅速减小；对合金挤压8道次后，得到晶粒细小、均匀分布的等轴晶组织，晶粒尺寸由铸态的45 μm减小至1.5 μm，此时，合金组织的细化趋于稳定，达到细化极限；晶粒细化机制是在往复挤压过程中通过累积动态再结晶，使再结晶得以彻底完成；增加位错密度和加剧晶界畸变使再结晶形核数目增多；大量挤压破碎、均匀分布的Mg₂Si第二相颗粒成为再结晶形核核心，从而使晶粒得以细化；往复挤压11道次时，由于挤压温度过高，导致晶粒发生异常长大，最大尺寸约为10 μm。本试验条件下晶粒发生异常长大的温度阀值约为400 ℃。

Abstract: The microstructures and grain refinement mechanisms of Mg-4Al-2Si (AS42) alloy by reciprocating extrusion (RE) were investigated. The results show that the dynamic recrystallization controlled by dislocation climbing occurs during the RE process. The grain size of the alloy decreases rapidly with increasing RE pass. The grain size of the as-cast alloy deceases from 45 μm to 1.5 μm after RE 8 passes, here the grain refinement is up to the limit. The mechanisms of grain refinement are that, during RE, the recrystallization is completed thoroughly by accumulative dynamic recrystallization, the nucleation numbers of recrystallization increases with increasing dislocation density and grain boundaries distortion severity, and the massive broken Mg₂Si particles become nucleating center of dynamic recrystallization, thus, resulting in the grain refinement. The grain begins to coarse up to 10 μm due to high temperature after RE 11 passes. Under the experimental conditions, the blow-threshold temperature of the grain coarse is about 400 ℃.

基金信息：陕西理工学院专项科研基金资助项目