新型Al-Cu-Li合金的热稳定性

Heat resistant properties of a new Al-Cu-Li alloy

通过热暴露后的室温拉伸和高温拉伸试验及透射电镜显微组织观察,研究1种新型Al-Cu-Li合金的热稳定性。结果表明:合金在T8峰时效态下室温拉伸强度为647 MPa,强化相为大量的T1相,部分θ′相和少量S′相,其中T1相起主要作用;在低于150℃下热暴露200 h后,T1相的密度和尺寸没有明显变化,二次析出少量θ′相,强度略有升高;在150℃热暴露500 h后,T1相略微长大,另有细小T1相析出,强度仅下降5%;在200℃和250℃热暴露200 h后,T1相显著粗化,且有粗大平衡相θ析出,力学性能快速下降;合金的高温拉伸强度随拉伸温度的升高而降低,在200℃下的抗拉强度为506 MPa,可达到常温时的87.7%,明显优于传统耐热铝合金。

Heat resistant properties of a new Al-Cu-Li alloy were studied through tensile test at room-temperature after long time thermal exposure, tensile test at elevated temperatures and TEM microstructures observation. The results show that the tensile strength of alloy at T8 peak age is 647 MPa. The strengthening phases are a large number of T1 phase, some θ′ phase and small amounts of S′ phase, and among them T1 phase plays the main role. After exposing at temperatures below 150 ℃ for 200 h, the density and size of T1 phase don’t change obviously and small amounts of secondary precipitation ofθ′can be observed, thus improving the tensile properties slightly. After exposing at 150℃for 500 h, T1 phase coarsens slightly and other tiny T1 phase is precipitated, so the strength decreases by only 5%. When exposing at 200℃and 250℃, T1 phase coarsens remarkably and large equilibrium phaseθis precipitated;as a result, the tensile property decreases rapidly. The tensile strength at elevated temperatures decreases when increasing test temperature. The tensile strength at 200 ℃is 506 MPa, reaching 87.7%of the strength at room temperature, which is much higher than those of traditional aluminum alloy used at elevated temperature.