Selective Laser Melting of Gas Atomized Al-3.02Mg-0.2Sc-0.1Zr Alloy Powder: Microstructure and Mechanical Properties

Additive manufactured Sc modified Al alloys for lightweight application is now arousing widespread attraction. The selective laser melting (SLM) of gas atomized Al-3.02Mg-0.2Sc-0.1Zr powder is studied, with the emphasis on its densification, microstructure, and properties. The intrigued finding is that the very high elongation-to-failure of 32.5% is obtained with medium tensile strength of 373MPa after heat treatment of SLM sample. The average relative density is about 98.3% at a volumetric energy density range of (VED) 42-111Jmm(-3). The microstructure of produced sample shows cracks but it can be inhibited by increasing the VED. At an excessive VED, the weld pool is transformed from heat conduction to keyhole mode owing to the metal evaporation. Nano-sized Al-3(Sc,Zr) precipitates with a diameter of 5-50nm are observed, which is responsible for the main strengthening mechanism. The underlying mechanisms of metallurgical defects, weld pool mode and mechanical properties are also illuminated.