Effect of direct aging treatment on microstructure, mechanical and corrosion properties of a Si-Zr-Er modified Al-Zn-Mg-Cu alloy prepared by selective laser melting technology

In this paper, a novel Al-Zn-Mg-Cu alloy with Si-Zr-Er addition was prepared by selective laser melting (SLM) technology. Effects of aging temperature and aging time on the microstructure, mechanical properties and corrosion resistance of the alloy were systematically studied. Results show that unique bimodal grain structure is formed in the as-printed and direct aging treated alloys, which is composed of fine equiaxed grains at the molten pool boundary and coarse columnar grains in the molten pool. Mechanical properties of the alloy can be improved by direct aging treatment, and the highest tensile strength reached 465 MPa. The precipitated Mg2Si and Al3(Er,Zr) with L12 structure play an important role in improving the mechanical properties. The precipitates and fraction of high-angle grain boundaries are important to evaluate the corrosion resistance of the investigated alloy. Considering the mechanical properties and corrosion resistance, the optimal aging process of the alloy studied in this paper is 150 °C × 4 h.