铸态及其均匀化组织
(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙 410083)
摘 要: 采用光学显微镜(OM)、X射线衍射(XRD)、差示扫描量热仪(DSC)和扫描电镜(SEM)及其附件能谱仪(EDX)研究Al-(7.8~9.0)Zn-1.6Mg-(1.0~2.2)Cu铝合金的铸态及其均匀化组织。结果表明： 该铝合金的铸态凝固组织由α(Al)基体+Mg(Zn, Al, Cu)2非平衡共晶相组成；铸态组织中粗大非平衡共晶组织的体积分数随着Zn含量的增加而增大，且伴随其周围析出的条状、细小Mg(Zn, Al, Cu)2粒子也逐渐增多、粗化；当Cu含量(质量分数)为1.0%、1.4%、2.2%时，铸态组织晶内的独立第二相分别为T(Al2Zn3Mg3)相、S(Al2CuMg)相、T(Al2Zn3Mg3)相+θ(Al2Cu)相；各成分合金经过(470 ℃, 24h)均匀化处理时，基体中仅剩下均匀化过程无法消除的尺寸较小、数量较少的初生富Fe相。
关键字: Al-Zn-Mg-Cu合金；铸态；均匀化；微结构
Al-(7.8-9.0)Zn-1.6Mg-(1.0-2.2)Cu aluminum alloys
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The microstructures of the as-cast and homogenized Al-(7.8-9.0)Zn-1.6Mg-(1.0-2.2)Cu aluminum alloys were studied by OM, XRD, DSC, SEM and EDX techniques. The results show that the as-cast microstructure of Al-(7.8-9.0)Zn-1.6Mg-(1.0-2.2)Cu aluminum alloy mainly consists of Mg(Zn, Al, Cu)2 phase and α(Al) matrix. The volume fraction of coarse eutectic-structure increases with Zn content increasing. Meanwhile, the accompanying precipitations of small Mg(Zn, Al, Cu)2 particles are also gradually increased. When Cu content(mass fraction) is 1.0%, 1.4% and 2.2% , the main second phases within grains are T(Al2Zn3Mg3) phase, S(Al2CuMg) phase and T(Al2Zn3Mg3)+ θ(Al2Cu) phases, respectively. The only remained particles in the matrix are some small Fe-rich particles after being homogenized at 470 ℃ for 24 h.
Key words: Al-Zn-Mg-Cu alloy; as cast; homogenization; microstructure
