Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 26    No. 4    April 2016

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Effect of T7951 secondary aging treatment on crack propagation behavior of 7055 aluminum alloy
Song ZHOU1,2, Lei WANG2, Li-yang XIE1, Li HUI2, Liang XU2

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

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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