Research On Processing,microstructure And Mechanical Properties Of Selective Laser Melting Of Mg-RE Alloy

Selective Laser Melting（SLM）is an emerging metal processing technologies that have been successfully applied to manufacturing traditional structural metal materials.In this research,SLM processing of Mg-RE alloys（GZ151K）and its composite materials systematically researched and the microstructures and mechanical properties of SLMed samples are systematically characterized.For SLMed GZ151K alloys,different processing parameters and corresponding different energy density result in different microstructures,defects types and defects distribution.In parameters that are not optimized,most common defects categories include cracking,round holes,lack of fusion and irregular shapes.After processing parameter optimization,defects-free GZ151K samples are obtained under parameter combination P200-V900-HS70,which consists of ultra fine equiaxed grains without strong textures.The phase constitution of SLMed GZ151K samples is Mg matrix,Mg₃Gd and Gd H₂.The as-fabricated SLMed GZ151K samples have yield strength（YS）of 314 MPa,ultimate tensile strength（UTS）of395 MPa and elongation of 2.7%.After peak-aged hardening,the YS,UTS and elongation increase to 385 MPa,406 MPa and 3.7%respectively,exhibiting better comprehensive mechanical properties compared with casting GZ151K alloys.By using optimized processing parameters for GZ151K/B composites,defects-free composite samples are obtained.Strengthening particles with size ranging from 1 to 2 widely disperse in matrix.On the boundary between strengthening Boron particles and matrix,in-situ formed block-shaped Gd-B phase are found.The tensile test results show that SLMed GZ151K/B composite exhibits a YS of 327 MPa,UTS of 344MPa and elongation of 2.3%,the elastic modulus is 52.5 GPa,which is 7.5GPa higher compared with SLMed GZ151K alloys.