Research On Laser Selective Melting Forming And Heat Treatment Process Of Invar36 Alloy

Invar36 alloy is a material with a very low thermal expansion coefficient,but due to its low processability and high density,its application range is severely limited.The Selective Laser Melting(SLM)process can form parts with complex structures,and has the advantages of small grains,uniform structure,and excellent mechanical properties.Therefore,it is of great significance to study the forming and performance control technology of Invar36 alloy SLM.Aiming to the Invar36 alloy material,the influence of forming process parameters on the density,microstructure,mechanical properties and thermal expansion coefficient of SLM forming Invar36 alloy.have been studied in this paper.The optimized forming process parameters of the Invar36 alloy SLM are obtained:laser power 300W,scanning speed 800mm/s,scanning distance 0.15mm,powder layer thickness 0.03mm.The properties of the as-deposited samples obtained by forming are anisotropic.The specific properties are:vertical direction(Z)tensile strength 384.5MPa,yield strength 327.5MPa,elongation 35.5%,cross-section hardness140.8HV;horizontal direction(H)The tensile strength is 457.5MPa,the yield strength is369MPa,the elongation is 28%,and the section hardness is 135.67HV;the thermal expansion coefficient of the sample is lower than 1.5×10^-6/?.On this basis,the effects of different heat treatment processes on the structure and properties of Invar36 alloy have been studied.The test results show that the mechanical properties after annealing at 400°C for 2h are the best.Compared with the deposited state,the vertical direction(Z)resistance The tensile strength is425.5MPa,an increase of 10.7%,and the yield strength is 348.5MPa,an increase of 6.4%;the horizontal direction(H)tensile strength is 465.5MPa,an increase of 1.7%,and the yield strength is 389.5MPa,an increase 5.7%.At the same time,the anisotropy difference of the formed part after annealing process is reduced.The mechanical properties of the formed parts are not significantly improved by the quenching process.Finally,for the Invar36 alloy complex lattice structure,the optimized process parameters have been used to carry out the forming process test,and the internal defects of the formed workpiece haved been detected.The results showed that the formed Invar36 alloy complex lattice structure had no Obvious defects,can meet the needs of use.