中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 20 No. 12 December 2010 |
AA 7055 aluminum alloy
（1. Beijing Institute of Aeronautical Materials, Beijing 100095, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China）
Abstract:The effects of precipitates on the fatigue crack growth rate of AA 7055 Al alloy subjected to different ageing treatments were investigated using transmission electron microscope and fatigue crack growth testing. The results show that the T77 treated samples exhibit the lowest crack growth rate, while the crack growth rate of over-aged samples is the highest. In terms of the model based on the reversibility of dislocation motion within the plastic zone close to the crack tip, the improved crack growth resistance is attributed to many precipitates that are coherent with Al matrix in the under-aged and T77 treated samples. When the precipitate is coherent with the Al matrix, the larger the precipitate is, the slower the fatigue crack grows. The effects of grain boundary precipitates and precipitate free zone on the fatigue crack growth resistance are less significant than those of precipitates within grains of the alloy.
Key words: 7055 aluminum alloy; ageing; fatigue crack growth rate; precipitate
