(1. 重庆大学 材料科学与工程学院，重庆 400044；2. 重庆市科学技术研究院，重庆 401123)
摘 要: 研究750、800、850、900和950 ℃不同熔体过热处理温度对AZ31镁合金凝固组织的影响规律。利用光学显微组织定量分析经不同温度过热处理所得AZ31镁合金的二次枝晶间距等组织特征差异；开发一种采用能谱分析结果计算Mg、Al和Zn等主要元素在一个枝晶单元内各个特征区域质量分数的方法，用以测评不同过热温度下凝固组织的成分均匀性。结果表明：当过热温度从750 ℃增加到900 ℃时，成分偏析减少，铸态组织中二次枝晶间距从13 μm减小到9 μm，多点随机显微硬度的平均值从36.5 HV增大到42.6 HV；AZ31镁合金较理想的熔体过热处理温度为900 ℃。
关键字: AZ31镁合金；过热处理；凝固组织；枝晶间距；成分偏析
solidification microstructure of AZ31 magnesium alloy
（1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. Chongqing Academy of Science and Technology, Chongqing 401123, China）
Abstract:The effect of different overheating temperatures on the solidification microstructure of AZ31 magnesium alloy was investigated. The overheating temperatures of 750, 800, 850, 900 and 950 ℃ were applied. The secondary dendrite spacing of AZ31 magnesium alloy at different overheating temperatures was quantitatively investigated through the optical microstructures. A method was developed to analyze the mass fraction of Mg, Al and Zn elements in each region of a dendrite cell by scanning electron microscope with energy spectrum, which was used to assess the component homogenization of the solidification microstructures at different overheating temperatures. The results show that with the increase of overheating temperature from 750 to 900 ℃, the chemical composition segregation is reduced, the secondary dendrite spacing is decreased from 13 to 9 μm, and the average value of multi-point random microhardness is increased from 36.5 HV to 42.6 HV. The better melt overheating temperature of AZ31 magnesium alloy is 900 ℃.
Key words: AZ31 magnesium alloy; superheating treatment; solidification microstructure; dendrite spacing; composition segregation
