2099铝锂合金微观组织及性能Microstructures and properties of 2099 Al-Li alloy

采用力学性能测试和透射电镜观察的方法，研究 2099 铝锂合金不同时效状态下的拉伸性能、应力腐蚀性能以及微观组织。结果表明：在欠时效条件下，合金抗拉强度、屈服强度和伸长率分别为453 MPa、382 MPa和12.5%，基体中形成大量的δ′相；峰时效条件下，大量的T1 相以及少量的θ′相在基体中析出，晶界上生成一定数量的第二相，并 形成无沉淀析出区，合 金相应的抗拉强度、屈 服强度和伸长率分别为613 MPa、5 81 MPa和7.9%；过时效条件下，合金抗拉强度、屈服强度和伸长率分别为610 MPa、570 MPa 和7.8%，其微观组织与峰时效合金的相似。在欠时效合金中，由于晶界上残余AlCuFeMn 相的存在，从而导致合金具有较高的应力腐蚀敏感性；在峰时效合金中，由于大量的 T1 相在基体中析出，促使合金获得理想的抗应力腐蚀性能，强度损失率为 0.8%；过时效合金具有与峰时效合金相近的抗应力腐蚀性能。

Tensile properties, stress corrosion properties and microstructures of 2099 Al-Li alloy under different aging conditions were investigated by mechanical tests and TEM. The results show that, under the underaged condition, the tensile strength, yield strength and elongation of alloy are 453 MPa, 382 MPa and 12.5%, respectively, and many δ′ phases form in the alloy. Under the peakaged condition, a great number of T1 phases as well as a few of θ′ phases precipitate in the matrix, some secondary phases precipitate along the grain boundaries and the precipitation free zone form, the corresponding tensile strength, yield strength and elongation of alloy are 613 MPa, 581 MPa and 7.9%, respectively. Under the overaged condition, the tensile strength, yield strength and elongation of alloy are 610 MPa, 570 MPa and 7.8%, respectively, and the microstructures are similar to that of peakaged alloy. Remained AlCuFeMn phases at grain boundaries result in high SCC susceptibility of underaged alloy. Peakaged alloy obtains desirable stress corrosion resistance because many T1 phases precipitate in the matrix, and the strength loss rate is 0.8%. Overaged alloy obtains similar stress corrosion resistance as peakaged alloy.

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