中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 18 No. 4 August 2008 |
（1. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
3. Department of Mechanical and Electrical Engineering, Changsha University, Changsha 410003, China）
Abstract:The effect of stress on the microstructure and properties of an Al-Cu-Mg-Ag alloy under-aged at 165 ℃ for 2 h during thermal exposure at 200 ℃ was investigated. The tensile experimental results show that the remained tensile strength of both specimens at room temperature after being exposed at 200 ℃ with and without applying stress rises firstly, and then drops with the increasing of exposure time. The peak value of the remained strength reaches 439 MPa for non-stress-exposure for 10 h, and 454 MPa after being exposed with stress loaded for 20 h at 220 MPa. The elongation change is similar to that of strength. After being exposed for 100 h, specimen exposed at 220 MPa still remains a tensile strength of 401 MPa, larger than that exposed without applying stress. TEM shows that the microstructure of under-aged alloy is dominated by Ω phase mainly and a little θ′ phase. The θ′ and Ω phases are believed competitive with increasing exposure time. The width of precipitation free zone(PFZ) increases and the granular second phase precipitates at grain-boundary correspondingly. It is shown that the mechanical properties of alloy decrease slightly and present good thermal stability after thermal exposure at 200 ℃ and 220 MPa for 100 h.
Key words: Al-Cu-Mg-Ag alloy; thermal exposure; stress; microstructure; mechanical properties
