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研究了2090、8090铝锂合金,7075、2024普通铝合金的疲劳裂纹扩展速率,门槛值,裂纹闭合效应,裂纹偏转特性和形貌,并讨论了上述各因素之间的内在联系。结果表明:在强度水平相近时,铝锂合金的疲劳裂纹扩展抗力明显优于普通铝合金,主要归因于其裂纹闭合和裂纹偏转的裂尖屏蔽(Shiekding)作用。铝锂合金特有的断裂特征(脊骨状断口)和强的氧化倾向,使之获得了高的粗糙度诱发裂纹闭合效应和氧化物诱发裂纹闭合效应。最后,本文还较系统地讨论了扁平晶粒、强织构、平面滑移、沿晶稳定相等对铝锂合金断裂特征、裂尖屏蔽效应等的影响。
The fatigue crack growth rate, the threshold value, crack closure effect, crack deflection characteristics and morphology of 2090, 8090 Al-Li alloys, 7075 and 2024 common aluminum alloys were studied. The intrinsic relationships between these factors were also discussed. The results show that the fatigue crack propagation resistance of Al-Li alloy is obviously better than that of common Al alloy at the similar strength level, which is mainly due to the Shiekding effect of crack closure and crack deflection. The unique fracture characteristics of aluminum-lithium alloy (fracture of the spine) and strong oxidation tendency make it obtain high roughness-induced crack closure effect and oxide-induced crack closure effect. Finally, the effects of flat grains, strong texture, plane slip and stable intergranular stability on the fracture characteristics of Al-Li alloy and the crack tip shielding effect are also systematically discussed.