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Advances in Materials Science and Engineering
Volume 2016, Article ID 7671530, 7 pages
http://dx.doi.org/10.1155/2016/7671530
Research Article

Influence of Grain Boundary on the Fatigue Crack Growth of 7050-T7451 Aluminum Alloy Based on Small Time Scale Method

Science & Technology on Reliability & Environmental Engineering Laboratory, Beihang University, Beijing 100191, China

Received 25 March 2016; Accepted 16 June 2016

Academic Editor: Liviu Marsavina

Copyright © 2016 Weihan Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Based on the small time scale method, the influence of grain boundary on the fatigue crack growth of 7050-T7451 has been investigated. The interaction between fatigue crack and grain boundary was investigated by in situ SEM testing. Results showed that the fatigue crack growth will be retarded by grain boundary when the angle between fatigue crack and grain boundary is greater than 90 degrees. Mechanism analysis showed that the fatigue crack tip would not be able to open until the loading reached the 55% of maximum load, and the fatigue crack had been closed completely before the loading was not reduced to the minimum value, which led to the crack growth retardation. When the 7050-T7451 aluminum alloy suffered from fatigue loading with constant amplitude, a behavior of unstable fatigue crack growth could be observed often, and results indicated that the bridge linked mechanism led to the behavior. The grain boundary was prone to fracture during fatigue loading, and it became the best path for the fatigue crack growth. The fatigue crack tip would be connected with fractured grain boundary eventually, which led to the fast crack growth in different loading stage.