Preparation And Microstructure And Mechanical Properties Of Laser 3D Printed Aluminum Alloy Lattice Materials

This paper studies the printing process and mechanical properties of pyramid AlSi10Mg l alloy lattice materials prepared DMLS(direct metal laser sintering)3D printing technology,and explores the 3D printing process parameters of different laser.The microstructure and microhardness of the printed AlSi10Mg Al alloy lattice structure materials under the condition of printing state and heat treatment process,including the quasi-static compression under normal working conditions and the dynamic compression properties under impact load,the results are as follows:(1)The optimum 3D printing parameters obtained are:ambient temperature 80℃,powder layer thickness 30μm,laser beam diameter 80μm,laser energy 370 W,laser scanning speed1300 mm/s.The AlSi10Mg aluminum alloy lattice structure material printed with this parameter has few hole defects and high compactness,the microstructure presents a layer-by-layer staggered stacking laser melting pool,which is composed of fineα-Al equiaxed grains and spherical Si granular phases.(2)After heat treatment,the molten pool morphology of a layer of staggered stacking formed by its laser scanning trajectory disappeared completely,and the heat-affected zone disappeared,which became a microstructure with uniform distribution of fine particle phase.With the further extension of the heat treatment process,the fine globular Si particle phases grown from nanoscale to bulk or acicular micron levels uniformly distributed on theα-Al matrix in the protoccytial intergranular nuclei and aggregated and precipitated.(3)The microhardness curve change of DMLS printed AlSi10Mg aluminum alloy solid material is similar to that of lattice structure material.Its overall hardness is higher than that of lattice structure material.the hardness peak value reaches 112.323 HV,but the magnitude of the rapid decrease of hardness is twice as much as that of lattice structure material(15%).However,DMLS laser 3D printing AlSi10Mg aluminum alloy solid material in the later stage of heat treatment decreases slowly.(4)DMLS quasi-static compression experiment of printed AlSi10Mg aluminum alloy lattice structural materials,the stress-strain curve can be divided into three stages:elastic stage,platform stage,densification stage.During the platform stage,the increase of strain leads to the increase of compressive stress;in the densification stage,the initial strain increases with the prolongation of the holding time.After heat treatment,the required compressive strength of lattice structural materials decreased from 45.74 MPa to 35.89 MPa,the platform stress decreased from 12.37 MPa to 8.76 MPa,and the platform area gradually became longer,the required compressive stress decreased from 11.25 MPa to 8.02 MPa,and the elastic gradient also decreased from 1.10 MPa to 0.90 MPa.Also found that the regulation of heat treatment temperature 2h lattice structure material compressive strength(39.75 MPa)to the provisions of the specific heat insulation processing 1h compressive strength(37.12 MPa),because when the time of heat treatment reaches 2h,Si particles precipitate almost completely,get the whole Si particles small,uniform phase distribution on theα-Al matrix,so the highest AlSi10Mg alloy lattice structure of the material strength.(5)The dynamic compression stress-strain curves of DMLS printed AlSi10Mg lattice materials are subjected to impact loading and can be divided into four stages:linear elastic deformation stage,elastic-plastic stage,softening stage,and densification stage.After the curve reaches the peak value,the compression stress value quickly drops to the lowest point,appears to soften,and presents the obvious fluctuation,then slowly rises,and the greater the applied pressure,the more obvious the fluctuation is.It is speculated that the failure mode of the component is mainly matrix cracking and fiber fracture,and the greater the pressure,the more obvious the cracking.And for the impact compression,the greater the applied pressure,the greater the platform stress,and the strain at the beginning of the compaction stage gradually increases.the strain rate of AlSi10Mg lattice structure material in the original state is higher than500℃/1 h at the same pressure,and the compression strain rate curve coincidence degree of both is very high at 1.5 MPa,which indicates that the lattice structure material after heat treatment can adapt to the compression experiment at higher strain rate.As the applied pressure increases,the peak value of the dynamic compressive stress-strain curve in the original 3D print state as well as in the heat treatment process conditions becomes larger,indicating that the increase of the compressive strain rate under impact load results in a larger compressive stress,and the buffer characteristics may be better.The curve elastic maximum compressive stress value(58 MPa)after heat treatment is lower than the original component(74 MPa)at 0.6 MPa,but the elastic maximum compressive stress value after heat treatmentσ_e,increases sharply with the impact load,and exceeds the original component,and the stress-strain curve coincidence degree before and after heat treatment is extremely high at 1.2 and 1.5 MPa,AlSi10Mg lattice materials after heat treatment may be more suitable for compression experiments at high strain rates.