Al-Mg-Sc-Zr alloy were prepared by selective laser melting (SLM) technology with gas atomization powders as raw materials. The effects of processing parameters on metallurgical defects, microstructure, and tensile properties of SLM-fabricated samples were investigated through optical microscope analysis, scanning electron microscopy analysis, and unidirectional tensile test at room temperature, etc. The results show that SLM-fabricated Al-Mg-Sc-Zr alloy is characterized with mixed grains structure in which fine equiaxed grains and coarse columnar grains alternate. It can be obviously found that element segregation in fine equiaxed grain region and precipitated Al3(Sc,Zr) particles pin at the grain boundary. When the laser power increases from 260 W to 380 W, the porosity of the sample decreases first and then increases, while the changing trend of mechanical property is opposite. When the laser power is 300 W, the optimum parameter is obtained with the relative density reaching 99.4%. There are only a few small shrinkage pores in the sample due to the insufficient supply of liquid metal. The ultimate tensile strength, yield strength, and fracture elongation are 429.7 MPa, 363.5 MPa and 17.7%, respectively. After aging treatment at 325 ℃ for 10 h, the ultimate tensile strength, yield strength, and fracture elongation are 530.1 MPa, 506.4 MPa and 9.0%, respectively.
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