Study on the Effect of Remelt Scanning and Heat Treatment Processes on the Structure and Properties of Laser Powder Bed Fusion Formed Al-Mg-Sc-Zr Alloys

Laser Powder Bed Fusion (LPBF) technology was used to form Al-Mg-Sc-Zr alloys to investigate the effects of remelting scanning and heat treatment processes on their tissue evolution and mechanical properties. The results show that the surface roughness (Sa) of the upper surface of the unmelted and once-remelted scans are similar. In contrast, the surface roughness (Sa) of the upper surface of the twice-remelted scans is significantly higher. The surface roughness (Sa) of the specimen sides gradually increases with the number of scans. The Al-Mg-Sc-Zr alloy has a unique mixed crystal structure, with many Al 3 (Sc, Zr)-L12 precipitates precipitating at the melt pool boundary to promote the formation of fine equiaxed crystals. In contrast, the interior of the melt pool is a coarse columnar crystal structure due to the low precipitation of Al 3 (Sc, Zr)-L12 precipitates. After heat treatment, more Al 3 (Sc, Zr)-L12 precipitates will precipitate inside the melt pool. After the aging heat treatment, the specimens’ yield and tensile strength increased significantly while the elongation at break decreased.