Fabrication And Properties Of Selective Laser Melting Fe-Ni Based Functional Materials

Additive manufacturing technology has been widely used in the production of structural materials and devices,because it can realize the manufacture and light weight of complex shape devices.Due to microstructure-sensitive properties of functional materials,additive manufacturing technology has been limit to apply in functional materials field.In order to solve the molding process of complex shape and the demand of expansion characteristic,magnetic properties in structure-function integration materials.We use selective laser melting(SLM)technology to fabricate 4J32\1J85alloys after preparation of powder for SLM by air atomization,then,the influence of process parameters on the relative density,tensile strength,magnetic properties,and expansion coefficient was studied.It lays a technical foundation for additive manufacturing to fabricate structural-functional integrated devices with complex structures.The results:The powder prepared by gas atomization process was regular spherical.Two kinds of powders are composed of FCCγ(Fe-Ni)phase.The oxygen content of powder is between 120ppm~330ppm,D50 distributes 30~38μm.The apparent density of 4J32powder was 4.41 g/cm~3,the tap density was 5.67 g/cm~3.The apparent density of 1J85powder was 4.28 g/cm~3,the tap density was 5.83 g/cm~3.All characteristics of powders meet the demand of SLM equipment and process.The microstructure of SLM samples is composed of fine dendrites,which axial size is less than 2μm.There is mass density dislocation inside the grains.The SLM samples performed excellent mechanical properties,such as,tensile strength achieves483Mpa,yield strength achieves 328Mpa.But the elongation rate only achieves 30%.After solution and aging treatment,the residual stress is released and the plasticity is restored.Besides,there was significant anisotropy in mechanical properties.The SLM samples exhibit abnormally low average coefficient of linear expansion,after solution and aging treatment,it returned to normal standard.The relative density of SLM samples increase with the increase of the energy densityε,then tend to a constant value,then decreasing,when theεdistribution is35~38 J/mm3,the density is optimal.The SLM specimens were annealed at 1180°C for 4h,6h and 1200°C for 4h,and 6h.Completed recrystallization occurred,and coarse austenite grain structure was formed After four kinds of heat treatment.Coarse and fine grains were alternately distributed.The SLM samples performed excellent mechanical properties,such as,tensile strength achieves 715Mpa,yield strength achieves 582Mpa,there was significant anisotropy in mechanical properties.The SLM samples exhibit poor magnet properties,after the heat treatment,the initial permeability can reach 31.36 mH/m;the maximum permeability reaches 65.66 mH/m;the value of coercivity decreases to 3.93 A/m.