Effect of bimodal microstructure on the tensile properties of selective laser melt Al-Mg-Sc-Zr alloy

Selective laser melting (SLM) has become a promising manufacturing route for the aluminum alloy models and parts in automotive and aircraft industries. In this work, an Al-4.0Mg-0.75c-0.4Zr-0.5Mn alloy was fabricated by SLM and near-full densification (relative density 99.7%) was obtained. A fine equiaxed grain regions and columnar grain regions alternately distributed characteristic is observed in the as-fabricated sample. The results of microstructural analyses show that the rapid solidification process and the precipitation of Al3Mg2, Al-6(Fe, Mn), and Al-3(Sc, Zr) particles lead to the fine grain structure, which provides a combination of high yield strength and excellent ductility. The mechanical properties of the as-fabricated sample were analyzed based on the typical microstructural feature of a combination of coarse columnar grain regions and fine grain regions. The strengthening effect is mainly attributed to the grain boundaries and the effect of grain boundaries on yield stress is according with the classical Hall-Petch relationship. (C) 2019 Elsevier B.V. All rights reserved.