Process Optimization and Mechanical Properties of AlMgScZr Alloy Fabricated by Laser Powder Bed Fusion Using Coarse Powder

With the advancement of laser powder bed fusion (LPBF) additive manufacturing, efficient utilization of powders outside the conventional particle size range (15–53 μm) has become critical to improving powder efficiency. This study investigated process optimization, microstructure, and mechanical properties of coarse AlMgScZr alloy powders (53–150 μm) in LPBF. The controlled variable method was employed to analyze parameter effects on density, defects, microstructure, and mechanical properties. Results show that the coarse powder exhibits a narrow process window with high sensitivity of forming stability to parameter fluctuations. The optimized parameters are a layer thickness of 100 μm, a laser power of 450 W, and a scanning speed of 900 mm/s. This parameter set achieves a relative density of 99.3%±0.2%. Microstructural analysis reveals fine equiaxed grains near fusion boundaries transitioning to columnar grains within molten pools, without observable secondary precipitates. The as-printed samples show a microhardness of 99.7±8.9 HV0.1, tensile strength of 336.5±8.0 MPa, and elongation of 12.7%±0.4%.