分级均匀化处理对7068新型高强铝合金组织及性能的影响

Effect of Three-step Homogenization on Microstructure and Mechanical Properties of 7068 Aluminum Alloy

采用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)及差热分析(DSC)研究了7068高强高韧铝合金均匀化热处理制度及其微观组织演变;通过单向拉伸试验及四探针电阻率法测定了不同均匀化后T6态合金的拉伸性能及电导率。结果表明:7068铝合金铸态组织存在枝晶偏析,非平衡共晶相沿晶界呈连续网状分布,低熔点共晶相初始溶解温度为467.3°C;合金经455°C×16h+465°C×4h+475°C×4h三级均匀化处理后,成分均匀,残留共晶很少且T6态的抗拉强度、延伸率以及电导率均达到所做均匀化处理中最佳,分别为715MPa、13.3%和34.5%IACS。

The paper presented the effect of homogenization heat treatment on microstructure of 7068 aluminum al oy using OM,SEM-EDS and DSC;it highlighted tensile properties and conductivity of the al oy in the T6 state after three-step homogenization. The results indicated that before homogenization：dendritic segregation in as-cast microstructure, nonequilibrium eutectic phase distribution along the grain boundary,467.3℃for initial temperature of eutectic phase dissolution;after the homogenization processes of 455℃×16h＋465℃×4h＋475℃×4h：uniform in composition,tiny eutectic structures;the tensile strength,elongation and conductivity respectively reached 715MPa,13.3% and 34.5%IACS,an optimal state in homogenization .