2099鋁鋰合金微觀組織及性能Microstructures and properties of 2099 Al-Li alloy

采用力學性能測試和透射電鏡觀察的方法，研究 2099 鋁鋰合金不同時效狀態下的拉伸性能、應力腐蝕性能以及微觀組織。結果表明：在欠時效條件下，合金抗拉強度、屈服強度和伸長率分別為453 MPa、382 MPa和12.5%，基體中形成大量的δ′相；峰時效條件下，大量的T1 相以及少量的θ′相在基體中析出，晶界上生成一定數量的第二相，并 形成無沉淀析出區，合 金相應的抗拉強度、屈 服強度和伸長率分別為613 MPa、5 81 MPa和7.9%；過時效條件下，合金抗拉強度、屈服強度和伸長率分別為610 MPa、570 MPa 和7.8%，其微觀組織與峰時效合金的相似。在欠時效合金中，由于晶界上殘余AlCuFeMn 相的存在，從而導致合金具有較高的應力腐蝕敏感性；在峰時效合金中，由于大量的 T1 相在基體中析出，促使合金獲得理想的抗應力腐蝕性能，強度損失率為 0.8%；過時效合金具有與峰時效合金相近的抗應力腐蝕性能。

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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