Abstract: Influence of heat treatment on microstructure and mechanical properties of spray formed 7A50 aluminum alloy was investigated. The microhardness and mechanical properties were tested. The OM, SEM(EDS) and TEM(SAED) were used to characterize the microstructure. The results indicate that the dendrite grains in the spray formed 7A50 aluminum alloy are eliminated, and the grain size reaches 60-120 μm. Pre-aging (PA) treatment enhances the initial hardness of the alloy and decreases the hardening rate during the natural aging (NA) process. Compared to the solid solution treated (SS)+NA state, the final hardness decreases by 19 HV0.5 after 12 days NA process. Under the SS+PA+NA+bake hardened (BH) conditions, the yield strength and tension strength of the alloy reach their peak values 475 MPa and 525 MPa respectively, the BH value of yield strength is 165 MPa, while the elongation decreases by 10%. Under different heat treatment conditions, the fracture morphologies all show ductile characteristics and have a large number of dimples. After SS+PA+NA treatment, the secondary phase in the matrix is dispersed and fine, with the size ranging from 5 nm to 15 nm.

Key words: spray formed, 7A50 aluminum alloy, microstructure, heat treatment, properties