Unveiling the SLM process-structure-property relationship of a moderate Mg content Al-Mg-Si-Sc-Zr-Mn alloy

Selective Laser Melting (SLM) holds great promise for fabricating high-precision aluminum alloy components with complex geometries and lightweight structures. However, producing high-strength aluminum alloys with excellent mechanical properties remains hindered by poor printability and complex microstructural control. In this study, an Al-4.79 Mg-1.3Si-0.51Sc-0.27Zr-0.47Mn (wt.%) alloy was developed and processed via SLM. The SLM process-structure-property relationship of this alloy was investigated. Crack-free samples were achieved across a broad process window, indicating excellent crack resistance and adaptability. Good printability and high relative density over 99.5 % can be achieved at a laser power of 200-230 W and scanning speed of 1050 and 1150 mm/s, corresponding to a volumetric energy density (VED) of 60 J/mm³-73 J/mm³. The increase in the laser energy density promoted the formation of columnar grains and the widening of subgrain structures, and made the Mg₂Si phase transformed from continuous to discontinuous morphology. The as-printed alloy exhibited 439 MPa tensile strength and 11.3 % elongation, attributed to grain refinement, reduced porosity, and the formation of the high dislocation density, 9R phase, and nanotwin. After aging, strength increased to 483 MPa and elongation decreased to 6.5 %. This study defines the process window and demonstrates a balance between high specific strength and cost efficiency.