采用显微维氏硬度计﹑拉伸试验机﹑扫描电镜和透射电镜研究了多级热处理工艺对铸造Al-Mg-Si-Sc-Zr合金组织与性能影响.结果表明:在固溶温度 575℃下,随着时间的延长,在晶界上呈网状分布的长条状Mg2Si转变为颗粒状的Mg2Si;对于Al3(Sc,Zr)相来说,最佳的高温时效制度为 320℃×1 h,热处理后的基体中有大量的纳米尺寸的Al3(Sc,Zr)相,可显著强化基体;对于时效析出相来说,随着低温时效温度的升高,时效析出相由GP区向β''相转变.经优化热处理后的铸造Al-Mg-Si-Sc-Zr合金的屈服强度﹑抗拉强度和伸长率分别达到 197.8 MPa﹑288.2 MPa﹑13.3%,对应的热处理工艺为:575℃×0.5 h+320℃×1 h+120℃×46 h.
Influence of Heat Treatment Process on Microstructure and Properties of Cast Al-Mg-Si-Sc-Zr Alloy
By using micro-Vickers hardness test,uniaxial tensile,and microstructure characterization by scanning electron microscope(SEM)and transmission electron microscope(TEM),the effects of heat treatment process on the microstructure and mechanical properties of Al-Mg-Si-Sc-Zr alloy were studied.The results show that the long strip Mg2Si with a mesh distribution at the grain boundary transforms to granular Mg2Si with the increase of hold time during solution treatment(575℃).As for Al3(Sc,Zr)particle,the optimized high-temperature aging treatment is 320℃×1 h.A large amount of nano-sized Al3(Sc,Zr)particles can be observed in 320℃×1 h treated alloy,which could significantly strengthen the matrix.As for aging induced precipitates,the aging precipitated phase changes from GP zone to β"phase with the increasing low-temperature aging temperature.The heat treatment process showing the best comprehensive mechanical properties in the uniaxial tensile test is 575℃×0.5 h+320℃×1 h+120℃×46 h,and the corresponding yield strength,tensile strength and elongation are 197.8 MPa,288.2 MPa and 13.3%,respectively.
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