Relation between heat treatment processes and microstructural characteristics of 7075 Al alloy fabricated by SLM

7075 aluminum alloy fabricated by selective laser melting (SLM) was subjected to different heat treatment processes. Microstructures and precipitates of this alloy were observed and analyzed under different treatment processes. The results indicated that there were shrinkage and porosity on the top surface of as-received alloys, and the undissolved coarse second phase distributed in the grain boundary. After a solution treatment, the grains re-nucleated and grew into some fine equiaxed crystals, and the rod-shaped Al3Ti and Mg2Si phases were also precipitated. After solid solution plus aging treatment, the grains continued to grow, and the Al3Ti phase disappeared. However, the finer theta (Al2Cu) phase and S (Al2CuMg) phase precipitate in the matrix. As a result, the shrinkage and porosity decreased significantly. After solid solution plus natural aging treatment, the grain grows and a relatively large theta (Al2Cu) phase is precipitated from the GP zone.