(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 南京航空航天大学 材料科学与工程学院，南京 210016)
摘 要:
关键字: 7475铝合金；热暴露；力学性能；显微组织
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics,Nanjing 210016, China）
Abstract:The microstructures and tensile properties at different thermal exposure condition of 7475-T7351 alloy were studied by means of tensile test, OM and TEM analysis. The results show that when the thermal exposure temperature is higher than the second aging temperature of 7475-T7351 alloy, the strength drops dramatically and the elongation increases. When the alloy is thermal-exposed at 175 ℃ for 100 and 500 h, the strength decreases 29.7% and 40.4%, respectively. When the thermal exposure temperature is lower than the second aging temperature of the alloy and thermal exposure time is not so long, the tensile properties of the alloy have no change, but if the thermal exposure time is long, the tensile properties of the alloy will also decrease and the ductility also increase. For example, when 7475-T7351 alloy is thermal-exposed at 125 ℃ for 100 and 500 h, the strength decreases 0.9% and 3.2%, respectively, but when it is exposed at 150 ℃ for 100 and 500 h, the strength drops 11.4% and 19.0%, respectively. Coarsening of η′ (MgZn2) precipitates and widening of precipitate-free-zones (PFZ) should be responsible for the decay of 7475-T7351 alloy during thermal exposure condition.
Key words: 7475 aluminium alloy; thermal exposure; mechanical property; microstructure
