Effect of heat treatment on microstructure, mechanical properties and corrosion behavior of LACSed 7075 deposits

Laser-assisted cold spray presents advantages in the additive manufacturing of high-strength 7075 aluminum alloy. In this paper, four heat treatment methods, including T6, T73, RRA, and annealing, were employed to further improve the mechanical properties and corrosion resistance of LACSed 7075 deposits. The relationship between their microstructures and performances was systematically investigated as well. SEM, EBSD, XRD, and TEM were used to observe the microstructure evolution of deposits after heat treatments in detail. Tensile test, IGC test, and potentiodynamic polarization curve test were performed to evaluate their mechanical and corrosion performances. The results showed that the grain structure maintained its anisotropy despite abnormal grain growth and static recrystallization following the heat treatments. The matrix precipitates and grain boundary precipitates showed distinct morphologies (size and shape) after different heat treatments, which had major impacts on the deposits' performances. The test results revealed that the T6 and RRA samples achieved highest yield strength of approximately 470 MPa. The elongation ratio of the LACSed deposits was greatly improved after annealing. The T73 and RRA samples exhibited much better corrosion resistance than the other samples. The evidence verified that typical post-heat treatments are feasible for improving the performance of LACSed 7075 deposits.