Ce对高强和中强铝锂合金疲劳长裂纹扩展特性的影响

Influence of Ce on the Growth Behavior of Long Fatigue Cracks for High-Strength and Medium-Strength Aluminum-Lithium Alloys

本文研究高强（２０９０）和中强（８０９０）铝锂合金疲劳长裂纹扩展机制，并分别与普通高强（７０７５）和中型（２０２４）铝合金相对比，揭示了在Ｐａｒｉｓ区和Ⅲ区的外韧化机制，同时，研究了微量稀土元素Ｃｅ对两种铝锂合金疲劳长裂纹扩展特性的影响。研究工作表明，２０９０和８０９０铝锂合金的名义疲劳长裂纹扩展抗力分别显著优于７０７５和２０２４合金，在近门槛值区归因于裂纹闭合效应，Ⅲ区归因于分层韧化效应，Ｐａｒｉｓ区系因裂纹闭合效应与分层韧化效应的藕合。２０９０和８０９０合金的本征疲劳裂纹扩展抗力分别优于和劣于７０７５和２０２４合金，微量Ｃｅ可大幅度改善２０９０合金的本征疲劳裂纹扩展抗力，在８０９０合金中则产生有害的影响。

The growth behavior of long fatigue cracks for high-strength (2090)and medium-strength(8090)aluminum一lithium alloys was investigated and was compared with that of high-strength(7075)and medium-strength(2024)traditional aluminum alloys,respectively.The ex-trinsic toughness mechanisms in Paris and Ⅲ zone has been revealed.Furthermore,the influenceof minor rare earth element Ce on the growth behavior of Iong fatigue cracks for aluminum-lithi-um alloys 2090 and 8090 was studied. Nominal growth resistance of long fatigue cracks for alu-minum-lithium alloys 2090 and 8090 is superior to that for alloys 7075 and 2024, respectively,which is attributed to crack closure effect in near-threshold zone and to detamination toughnesseffect in Ⅲ zone,and extrinsic toughness effect in Paris zone comes from the unite effect of crackclosure and detamination toughness. Intrinsic growth resistance of fatigue cracks for alloy 2090 and8090 is superior and inferior to that for alloys 7075 and 2024,respectively. A significant improve-ment in the intrinsic growth resistance can be obtained by adding minor Ce into alloy 2090. On thecontrary,the harmful influence is exhibited by adding Ce into alloy 8090.