Microstructural morphology and mechanical properties of deep cryogenic treatment modified Al-Cu-Mg-Ag alloy

In order to develop high-strength Al-Cu-Mg-Ag alloys used in the aerospace, this paper studied the mechanical properties and microstructure of Al-Cu-Mg-Ag alloys with T6I4 secondary aging and T6I4 secondary aging combined with deep cryogenic treatment. The results show that deep cryogenic treatment can promote the nucleation and growth of S2 phase. After deep cryogenic treatment for 1 h, the distribution of S2 phases in the alloy matrix is uniform, the size is small, and the properties of the alloy are optimized. The deep cryogenic treatment can also introduce dislocations, which can promote the mechanical properties of the alloy. Compared with the T6I4 temper, the appropriate deep cryogenic treatment can improve the mechanical properties of the alloy. The improvement of the mechanical properties of the alloy is mainly due to the fact that the cryogenic treatment can promote the fine and uniform precipitation of more S2 phases. The mechanical properties of the AlCu-Mg-Ag alloy after deep cryogenic treatment for 1 h are promising, the hardness value is 157.4 HV, the tensile strength, yield strength and elongation are 513.3 MPa, 472.7 MPa and 11.6%, respectively.