Effect of low temperature on fatigue and crack propagation behavior of aeronautic aluminium alloy

Journal of Aeronautical Materials

LIU Mudong¹ 

[1] Rotor and Transmission Department, China Helicopter Research and Development Institute, Jingdezhen 333001, Jiangxi, China;

关键词: aluminium-alloy;    cryogenic;    fatigue;    crack growth;    micromechanism;   

DOI  :  10.11868/j.issn.1005-5053.2020.000024

来源: DOAJ

【 摘 要 】

Fatigue and crack growth tests were performed on two categories of the common aeronautic aluminum- alloys 2524-T3 and 7050-T7451 at ambient temperature of 25 ℃ and cryogenic temperature of –70 ℃, in order to investigate the fatigue and crack propagation properties and micro mechanism. The test results show that the cryogenic fatigue life under the same amplitude loading rises and cryogenic crack growth rate decreases, which demonstrates the beneficial effect of cryogenic temperature on fatigue and crack growth properties. Furthermore, the fractographic micro mechanism reveals significant cleavage facets appeared during fatigue crack initiation at the cryogenic temperature of –70 ℃, leading to a concavo-convex morphology on fracture surfaces, and the fatigue crack initiation becomes difficult. On crack growth zones, the fatigue striations and dimples become unobvious, while evident intergranulars are occurred. As a result, the local fatigue crack tends to propagate zigzag and intergranularly, and fatigue and crack growth lives are increased. With the increasing loading stress level, the concavo-convex morphology and ductile transgranulars are reduced, while the fatigue striations and dimples are increased on fatigue surfaces, which demonstrates the cryogenic effect on fatigue crack initiation and propagation becomes weaker. This results have important theoretical and practical value.

【 授权许可】

Unknown