Effects of a hybrid post-treatment on microstructure and mechanical properties of cold sprayed AA7050 deposits

Abstract

Cold spray additive manufacturing (CSAM) technology is a promising and efficient method for preparing high-strength aluminum alloy components. In this work, AA7050 deposits were prepared by high-pressure cold spraying, and a hybrid post-treatment (i.e., annealing + hot compression + solid solution and aging) was proposed to improve the mechanical properties of the deposits. The results of the study indicated that the annealing alone was insufficient to eliminate all defects within the AA7050 deposits. After annealing, the porosity of the material decreased from 2.34% to 1.62%. The subsequent hot compression and aging treatment promoted the precipitation of strengthening phases and homogenized the microstructure, reducing the porosity of the AA7050 deposits to 0.18%. As a result, the mechanical properties of the materials further improved. The ultimate tensile strength of the CSAMed AA7050 after aging treatment reached 557.7 MPa, which was 337.4% and 149.3% higher than that of the as-sprayed and annealed materials, respectively. Furthermore, fracture surfaces analysis indicated that the fracture mechanism of the specimens changed from brittle to ductile mode after the hybrid post-treatment.