ECAP对粗晶AZ31镁合金的晶粒细化机制的影响
Effect of Equal Channel Angular Pressing on Grain-refining Mechanism of Coarse-grained AZ31 Magnesium Alloy
严 凯, 孙扬善, 白 晶, 薛 烽
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作者单位：(东南大学 材料科学与工程学院, 江苏 南京 211189)
中文关键字：等通道转角挤压； 镁合金； 孪晶； 动态再结晶； 晶粒细化； 均匀性
英文关键字：ECAP; magnesium alloy; twinning; dynamic recrystallization; grain refinement; uniformity
中文摘要：采用等通道转角挤压(ECAP)方法对AZ31镁合金进行挤压加工，并研究了变形过程中试样各部位的显微组织和硬度的变化。显微组织分析表明，孪晶在剪切变形阶段可以协调晶粒变形，而且在变形后成为动态再结晶晶粒形成的中心。ECAP过程中AZ31镁合金的组织是以一种非均匀的方式细化的，再结晶晶粒主要在孪晶界上形核，这形成了双模态的晶粒分布。研究还发现，经过ECAP后的试样纵截面上部残留的大晶粒明显多于下部的，这是由于在静态再结晶阶段试样各部位受力状态的不同造成的，这很好地解释了ECAP不同路径对镁合金均匀性的影响。
英文摘要：Equal channel angular pressing (ECAP) was performed on AZ31 magnesium alloy and the microstructure and hardness distribution of the sample processed by ECAP was systematically studied. The results reveal that the twinning can coordinate grain deformation in the beginning of ECAP and provides the nucleation positions for the dynamic recrystallization in the later stage of ECAP. The grain refining mechanism of AZ31 magnesium alloy is inhomogeneity in the processing of ECAP because recrystallization nucleation mainly occurs in twin boundaries, which generates a bimodal grain size distribution. The big grains at the top of the sample are more than that at the bottom, and the difference of microstructure is caused by the variation of stress in the each position of the sample during static recrystallization, which cna explain the different ECAP routes affect the uniformity of Mg alloy.