Study On Microstructures And Mechanical Properties Of AlSi10Mg Alloy Produced By Selective Laser Melting

AlSi10Mg alloy which has excellent casting properties can precipitate Mg₂Si phase that can improve its strength after solution treatment and aging treatment.It is applied to cast medium-load parts with complex shapes,such as cylinder blocks and motor shells.However,traditional casting technology has some problems,such as high costs of die design,long production cycle,and limited shape of parts.Therefore,processing parameters,microstructures and mechanical properties of AlSi10Mg alloy prepared by selective laser melting?SLM?were studied in this work,and the effects of heat treatment on its phase distribution,microstructures and mechanical properties were also discussed,which aims to provide theoretical guidance for the production of complex Al Si10Mg alloy parts with high density and excellent properties by SLM.The optimum SLM processing parameters of AlSi10Mg alloy were determined.Laser power is 350W,scanning speed is 1100mm/s,scanning distance is 150um,powder layer thickness is 30um,and scanning strategy is 67 degrees rotated between two adjacent layers.The relationship among laser energy density,density and roughness is illustrated.The greater the laser energy density,the greater the density is,but the surface roughness also increases.In addition,the scanning speed has a remarkable influence on the phase and hardness of the alloy.With the increment of scanning speed,Al peak in XRD spectrum of the alloy is shifted to the right,and the hardness of the alloy increases.The scanning distance has a significant influence on the roughness of the alloy part.With the increment of scanning distance,the roughness increases firstly and decreases later.The phase distribution,microstructures,mechanical properties and fracture mechanism of AlSi10Mg alloy prepared by SLM were studied.Results show that the main phases of SLMed AlSi10Mg alloy are?-Al and Si phase.Besides,needle?"phase,spherical?Mg+Si?cluster/GP zone,and short columnar Si phase exist in the matrix grain as well as coarse grain region,fine crystal region and heat affected zone on XOY and XOZ surfaces with different distribution sequences.Besides,when the number of stacking layers on the XOZ surface increases,columnar dendrites in the alloy gradually turn to two sides of the sample and grow.Yield strength and plasticity of the horizontal sample are better than those of vertical specimen,which is mainly related to the flat shape of holes in the stacking layers.Different subsequent heat treatments were applied for SLMed AlSi10Mg alloy.Results show that the eutectic Si network becomes disconnected and the Si phase gathers and grows at the original network groove or angle after annealing.Annealing twins and many needle phases?meta-stable?"phase and?'phase?are found in the matrix grain.The plasticity of the specimen is improved,the strength decreases slightly,and the hardness is improved slightly.After T4 heat treatment,the eutectic Si network is completely dissolved and fractured.Only the massive Si and spherical?Mg+Si?cluster/GP regions are left in the matrix grain.The strength and hardness of the specimen are remarkably reduced,but its plasticity is obviously improved.After T6 treatment,the eutectic Si network is completely dissolved and fractured,and the bulk Si phase aggregates further and grows.In addition,needle?"phase precipitates on the Al matrix.The edge of holes becomes smooth and round,and some particles found at the bottom of holes are re-melted.The yield strength of samples slightly increases and its hardness is equal to that of samples without heat treatment.