Metallurgical and Tensile Properties of a Laser Powder Bed Fused Scandium-free Al–Mg–Zr Alloy

Abstract

In this study, an Al–Mg–Zr alloy was developed for laser powder bed fusion (LPBF) to fulfill the need for a cost-effective, high-strength additive manufactured (AM) aluminum alloy. To get to the peak strength a single-step aging treatment (6 h at 400 °C followed by gas quench) was conducted on the printed alloy. The quasi-static uniaxial tensile properties of aged LPBF Al–Mg–Zr were measured as yield strength (YS) of 390 ± 2 MPa, ultimate tensile strength (UTS) of 428 ± 2 MPa, and elongation to failure (EL) of 14.26 ± 0.94 %. Microstructure analyses via scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) displayed the presence of precipitates and a bimodal grain distribution with ultrafine (∼1 μm) and fine grains (∼5 μm). Detailed investigation through transmission electron microscopy (TEM) showed frequent precipitation of nanoscale L1₂-Al₃Zr along with sub-micron Mn- and Fe-rich precipitates (i.e., orthorhombic Al₆(Mn, Fe)) and nanoscale Mg- and O-rich particles. The work-hardening behavior of the studied LPBF Al–Mg–Zr alloy offered valuable insights into the connection between the microstructure and tensile properties.