中國(guó)有色金屬學(xué)報(bào)(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 26 No. 4 April 2016 |
（1. School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110004, China;
2. Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process,
Shenyang Aerospace University, Shenyang 110136, China）
Abstract:The crack propagation rates of T6 peak aging and T7951 secondary aging 7055 aluminium alloys were tested under stress ratios (R) of 0.6, 0.05 and -1, respectively. The microstructures and fracture surfaces were analyzed by TEM and SEM. The results reveal that the crack propagation rate is affected by the stress ratio and microstructure such as the distribution, dimension and volume fraction of matrix precipitates, grain boundary precipitates and precipitate free zone. For both heat-treated specimens, crack propagation rate increases with the improvement of R when it is a positive value while crack propagation rate at R=-1 is much similar to that at R=0.06. The crack growth rates exhibit no obvious difference in lower stress intensity factor range (ΔK), while the difference starts to be obvious when ΔK exceeds certain value. The fracture analysis testifies a better fracture toughness for 7055-T7951 with a smaller striation space in Paris region.
Key words: 7055 aluminum alloy; T7951 secondary aging; crack propagation; fracture surface morphology
