The Process Optimization And Heat Treatment Of Selective Laser Melting For Magnesium Alloy

Magnesium alloys have outstanding advantages such as high specific strength,specific stiffness,good thermal conductivity,shock resistance,excellent electromagnetic shielding,machinability and biocompatibility,and easy recycling.It is widely used in aerospace,defense and military,electronic products,biomedical,automotive industry and other fields.However,magnesium alloys are difficult to form complex members due to poor processability at room temperature,and conventional cast magnesium alloys often have casting defects,resulting in low yield and high cost.Selective Laser Melting(SLM)technology is a branch of additive manufacturing technology.This process does not require any tooling die and do not limited by the complexity of the shape.It could obtain good metallurgical bonding,high complexity of components.Firstly,this article establishes an oxygen barrier system based on the safety problems of magnesium alloys during sieving and transfer.Then,based on the previous research of the research group,the laser power and scanning speed are the target parameters for the magnesium alloy SLM forming process.The research was carried out and the experimental results were analyzed to determine the optimal process parameters.Finally,the effects of solid solution and solid solution+aging on the mechanical properties and microstructure of the as-deposited magnesium alloy were analyzed.The results show that:1)The oxygen isolation system can keep the oxygen concentration below 1%,which meets the experimental safety requirements.2)The influence of laser power on tensile strength is dominant and the influence is extremely significant,followed by scanning speed.Under the optimal parameters of laser power of90W and scanning speed of 400mm/s,the average tensile strength and elongation of the test specimens are 317.6MPa and 7.16%,respectively.The super-constant cast magnesium alloys are 38.09%and 138.67%,respectively,and the average density is 99.580%.3)After 6 hours of solid solution at 420°C,rhenium-Mg₁₇Al₁₂ is almost completely dissolved,the tensile strength is reduced to 292.6 MPa,and the elongation is increased to13.19%.Prolonging the solution time has no significant effect on the microstructure and mechanical properties.At 420°C for 6h+200°C for 2h,4h,6h,and 10h,the mechanical properties of the test specimens are generally lower than that of the deposited state,and the elongation is generally increased.Compared with the solution treatment,the tensile strength is increased.The elongation is reduced.