(1. 中南大學 材料科學與工程學院，長沙 410083；
2. 中南大學 有色金屬材料科學與工程教育部重點實驗室，長沙 410083)
摘 要: 采用力學拉伸性能測試和透射電鏡微觀組織觀察，分析欠時效態(tài)和峰時效態(tài)Al-Cu-Mg-Ag合金的熱穩(wěn)定性，并研究熱暴露溫度和時間對合金組織與力學性能的影響。結果表明：在150 ℃下，欠時效態(tài)合金的穩(wěn)定性能明顯優(yōu)于峰時效態(tài)合金的；峰時效態(tài)合金的抗拉強度隨著熱暴露時間的延長逐漸減小，合金中的強化相Ω相和少量的θ′相逐漸發(fā)生粗化；欠時效態(tài)合金的抗拉強度隨熱暴露時間的延長先增大后減小，合金組織中的析出相數(shù)量先增多后減少，并發(fā)生粗化；熱暴露20 h后，欠時效態(tài)合金的抗拉強度達到峰值524 MPa，比峰時效態(tài)合金的強度高19 MPa；此時，合金組織中的Ω相呈彌散分布，并且出現(xiàn)大量細小的θ′相；欠時效態(tài)合金在150 ℃下熱暴露1 000 h后，其抗拉強度減小為434 MPa，仍能達到峰時效態(tài)合金的86%；當熱暴露溫度升高至200 ℃時，隨熱暴露時間的延長，欠時效態(tài)合金的抗拉強度減小，伸長率增大；熱暴露1 000 h后，其抗拉強度降低到307 MPa；在250和300 ℃下熱暴露時，欠時效態(tài)合金的抗拉強度隨時間的延長急劇減小，組織中的強化相數(shù)量明顯減少，并逐步演變成粗大的平衡相θ相。
關鍵字: Al-Cu-Mg-Ag合金；熱暴露；欠時效；力學性能；顯微組織
（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
