(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: 采用力学拉伸性能测试和透射电镜微观组织观察，分析欠时效态和峰时效态Al-Cu-Mg-Ag合金的热稳定性，并研究热暴露温度和时间对合金组织与力学性能的影响。结果表明：在150 ℃下，欠时效态合金的稳定性能明显优于峰时效态合金的；峰时效态合金的抗拉强度随着热暴露时间的延长逐渐减小，合金中的强化相Ω相和少量的θ′相逐渐发生粗化；欠时效态合金的抗拉强度随热暴露时间的延长先增大后减小，合金组织中的析出相数量先增多后减少，并发生粗化；热暴露20 h后，欠时效态合金的抗拉强度达到峰值524 MPa，比峰时效态合金的强度高19 MPa；此时，合金组织中的Ω相呈弥散分布，并且出现大量细小的θ′相；欠时效态合金在150 ℃下热暴露1 000 h后，其抗拉强度减小为434 MPa，仍能达到峰时效态合金的86%；当热暴露温度升高至200 ℃时，随热暴露时间的延长，欠时效态合金的抗拉强度减小，伸长率增大；热暴露1 000 h后，其抗拉强度降低到307 MPa；在250和300 ℃下热暴露时，欠时效态合金的抗拉强度随时间的延长急剧减小，组织中的强化相数量明显减少，并逐步演变成粗大的平衡相θ相。
关键字: Al-Cu-Mg-Ag合金；热暴露；欠时效；力学性能；显微组织
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. The Key Laboratory of Nonferrous Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The thermal stability of Al-Cu-Mg-Ag alloys under-aged and peak-aged was analyzed by tensile test and transmission electron microscopy (TEM). And the effects of thermal exposure temperature and holding time on the microstructure and mechanical properties of Al-Cu-Mg-Ag alloy were also studied. The results show that the thermal stability of the under-aged Al-Cu-Mg-Ag alloy is superior to that of the peak-aged alloy when exposed at 150 ℃. The tensile strength of the peak-aged alloy decreases with prolonging the holding time. And the strengthening phases Ω and little θ′ are coarsened gradually. The tensile strength of the under-aged alloy increases and then decreases with prolonging the time. And the number of the precipitations increases and then decreases with the slowly coarsening of the precipitations. The tensile strength of Al-Cu-Mg-Ag alloy reaches the peak value of 524 MPa after exposed for 20 h, which is 19 MPa larger than that of the peak-aged alloy. Meanwhile the precipitations Ω distribute dispersively and a large amount of fine θ′ phase is observed. The tensile strength of the under-aged alloy is 434 MPa after exposed at 150 ℃ for 1 000 h, which is 86% of that of the peak-aged alloy. When exposed at 200 ℃, the tensile strength decreases and the prolongation increases with prolonging the exposure time. The tensile strength decreases to 307 MPa after exposed for 1 000 h. The tensile strength decreases dramatically with prolonging the holding time. And the number of the strengthening phases decreases obviously and grows to equilibrium phase θ.
Key words: Al-Cu-Mg-Ag alloy; exposure; under-aging; mechanical properties; microstructure
