Abstract: Effect of Ag and Sc combined microalloying on microstructure and high-temperature properties of Al-Cu-Li alloys was studied through mechanical property testing at 250 ℃ and 300 ℃ and microstructure analysis. The results show that the Al-Cu-Li alloy with Ag and Sc combined microalloying has high high-temperature mechanical properties at 250 ℃, and its tensile strength, yield strength and elongation are 340 MPa, 297 MPa and 11.1%, respectively. Microalloying with Sc instead of Ag makes Al-Cu-Li alloy have excellent mechanical properties at 300 ℃, and its tensile strength, yield strength and elongation are 325 MPa, 292 MPa and 9.3%, respectively. The main reason for improving the high-temperature strength of the Al-Cu-Li alloy at 250 ℃ is the large amount of the high temperature stable strengthening T₁ precipitates at the grain boundary and inside the grain. The Ag and Sc combined microalloying can refine the grain of the Al-Cu-Li alloy, and the as-cast microstructure of the Al-Cu-Li alloy can be further refined when microalloying with more Sc instead of Ag. The refined grain is more conducive to recrystallization, the high temperature holding promotes the coarsening of the recrystallized grain, and the recrystallized grain is deformed again by the secondary medium temperature hot rolling, so that the alloy has better high temperature strength and plasticity matching at 300 ℃.

Key words: Al-Cu-Li alloy, Ag and Sc combined microalloying, artificial aging, high temperature mechanical properties