Phase evolution and mechanical properties of Al-2.8%Cu-1.35%Li-0.11%Zr alloy under thermal coupling

TEM, HAADF-STEM and tensile tests were applied to investigate the evolution law of precipitated phases and mechanical property of Al-2.8%Cu-1.35%Li-0.3%Mn-0.11%Zr alloy under artificial ageing and creep stress ageing. The results showed that the number of precipitated phases of the alloy increased significantly with the extension of the ageing time during both the artificial ageing and stress ageing of 160 MPa at 160 ℃ and the number of alloy T₁ phrase in the state of stress ageing under the same ageing time, but its average diameter decreased by about 5~15 nm, mainly because the stress increased the dislocation density in the alloy, accordingly promoting the separation of precipitated phases. T₁ phrase was not affected by the applied stress during the process of ageing separation analysis, but preferentially precipitated along a certain direction. There was no obvious stress orientation effect, which may be related to the larger shaped nuclei on the habitual T₁ plane variant with critical stress values. Compared to artificial ageing, the yield strength and tensile strength of the alloy at room temperature increased after the stress ageing, and the effect on the yield strength is more significant in the early stage of the ageing.