(1. 中南大学 轻合金研究院,长沙 410083;
2. 中南大学 轻质高强结构材料重点实验室,长沙 410083;
3. 中南大学 有色金属先进结构材料与制造协同创新中心,长沙 410083)
摘 要: 利用Thermo-cale软件计算及OM、SEM、XRD、DTA等分析手段,对比研究几种高Zn型超强Al-Zn-Mg-Cu系合金的铸态与均匀化态组织。结果表明:高Zn低Cu含量的7037、7056、7097铝合金铸态组织中主要存在a(Al)+Mg(Zn,Cu,Al)2共晶组织,经多级均匀化热处理后非平衡结晶相基本溶解;高Zn高Cu含量的7095铝合金沿晶界呈网状分布的粗大凝固组织主要由a(Al)、Mg(Zn,Cu,Al)2相、T(AlZnMgCu)相以及少量的θ(Al2Cu)相组成,经均匀化热处理后,仅存在少量AlZnMgCu相;高Zn低Cu含量合金凝固及均匀化组织中非平衡结晶相少的主要原因是合金成分远离极限固溶度曲线。
关键字: Al-Zn-Mg-Cu系合金;相图计算;铸态组织;均匀化
(1. Light Alloy Research Institute, Central South University, Changsha 410083, China;
2. Science and Technology on High Strength Structural Materials Laboratory, Central South University, Changsha 410083, China;
3. Collaborative Innovation Center of Advanced Nonferrous Structural Materials and Manufacturing, Central South University, Changsha 410083, China)
Abstract:The microstructure in as-cast and homogenized Al-Zn-Mg-Cu alloys with high Zn ultra-high strength were investigated by thermo-cale software, OM, SEM, XRD, DTA. The results indicate that the as-cast microstructure of alloys 7037, 7056 and 7097 with high Zn low Cu content, in which eutectic microstructure mainly contains a(Al) and Mg(Zn,Cu,Al)2 after multi-homogenizing, the non-equilibrium crystalline phases are almost dissolved. The coarse solidification microstructure along the grain boundaries of 7095 alloy with high Zn, Cu contents is composed of a(Al), Mg(Zn,Cu,Al)2 phase, T(AlZnMgCu) phase and a small amount of θ(Al2Cu) phase, only some of AlZnMgCu phases still remains in matrix after being homogenized. The main reason for less non-equilibrium crystalline phases in aluminum alloys with high Zn low Cu content is that the composition of alloys is far from the limit of solubility curves.
Key words: Al-Zn-Mg-Cu alloys; thermodynamic calculation; as-cast microstructure; homogenization