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The Effect of Thermal Exposure on the Microstructures and Mechanical Properties of 2198 Al–Li Alloy

The effect of thermal exposure on the microstructure and mechanical properties of 2198 Al–Li alloy is investigated. It is found that thermal exposure will lead to deterioration of the strengths, except the one exposed at 200 °C. When exposure temperature increases to 300 °C, a dramatical drop in strength and a rise in ductility appear due to the dissolution of strengthening phases, T1 phase, and θ′ phase. The new phases, (Al2Cu), Al6Cu(Li,Mg)3, and Al6CuLi3 phases, are formed. Compared with the alloy exposed at 300 °C, the alloys exposed at 400 and 500 °C exhibit better mechanical properties due to the precipitation of δ′ phase. The fractographic observation shows that the predominant fracture mode changes from quasi‐cleavage fracture to ductile fracture with the increasing exposure temperature.