Microstructures and Mechanical Properties of Al-Mg-Sc-Zr Alloy Additively Manufactured by Laser Direct Energy Deposition

Abstract

An Al-Mg-Sc-Zr alloy was additively manufactured by laser direct energy deposition (DED) under different laser powers, and the microstructures and mechanical properties of the as-deposited samples were investigated. The samples showed a fully equiaxed grain structure with grain sizes of 2–30 μm. Most of the blocky primary Al₃(Sc, Zr)-precipitated phases (<5 μm) were arranged along the grain boundaries. A small amount of fine granular secondary Al₃(Sc, Zr) phases (<0.5 μm) were precipitated owing to the cyclic heat treatment during the DED forming process. According to the EBSD(Electron backscatter diffraction) results, the texture index and strength of the sample were only slightly greater than 1, indicating that the material structure exhibited a certain but not obvious anisotropy. The sample in the horizontal direction had better yield strength, tensile strength, and elogation properties (399.87 MPa, 220.96 MPa, 9.13%) than that in the building direction (385.40 MPa, 219.40 MPa, 8.24%), although the sample in the〈XOZ〉 plane had the finest equiaxed grains. The ductility of the 〈XOZ〉 sample deteriorated as the number of pores increased.