Study On Microstructure,properties,and Modeling Of AlSi10Mg Alloy By Selective Laser Melting

AlSi10Mg is widely used in mechanical processing,automobile manufacturing,aerospace and other fields because of its characteristics of low density,high strength,and good corrosion resistance.The traditional processing technology is difficult to meet the requirements of Al alloy parts with complex shape and structure which is induced by lightweight.SLM（Selective Laser Melting）selectively melts powder by high-energy laser beam,forming parts with complex shapes layer by layer.Therefore,in this thesis,AlSi10Mg alloy was formed by SLM,and the analysis of powder properties,the comparison of structure and properties of different sections of the formed alloy,the influence of annealing heat treatment on the structure and properties of the alloy,and the integration of molding and forming were carried out.In order to analyze whether the properties of AlSi10Mg powder meets the requirements of SLM forming for powder properties,a series of properties tests were carried out.The results showed that most of the AlSi10Mg powder were regular spherical shape with a good sphericity,accompanied by a small number of secondary agglomeration phenomenon and irregular shape particles.Al,Si,and Mg three elements were uniformly distributed,there were no obvious macro-segregation,the particle size presented a unimodal normal distribution,the particle size mainly distribution between 22.58～58.78μm.The apparent density of AlSi10Mg powder was 1.517 g cm^-3,the tap density was 1.695 g cm^-3,the fluidity was73 s/50g,the angle of repose was 32°,and the specific surface area was3.0456 m² g^-1.The properties of AlSi10Mg powder meets the SLM forming requirements.AlSi10Mg powder was formed by SLM,and the structure and properties of the formed AlSi10Mg alloy were analyzed.The results showed that the alloy mainly consisted ofα-Al and eutectic Si,and the molten pool was divided into fine grain zone,coarse grain zone,and heat affected zone.The XOY surface of the alloy was a columnar molten pool accumulation structure,which was dominated by equiaxed grains and formed{101}<100>Cube texture.The YOZ surface of the alloy was a fish-scale molten pool accumulation structure,mainly consisted of columnar grains and formed{111}<110>Brass R texture.The tensile properties and micro-hardness of the alloy were higher than those of traditional casting AlSi10Mg alloy,and the micro-hardness of XOY surface was higher than that of YOZ surface.The structure and properties of different sections of the alloy were different,and there was anisotropy.The AlSi10Mg alloy was annealed to explore the law of heat treatment process on the structure evolution and properties change of the alloy.The results showed that with the increase of annealing temperature,the network eutectic Si gradually fractured and dissolved,forming fine Si particles,and the fine Si particles further coarsened and spheroidized,fine grain strengthening and solid solution strengthening were weakened,and the casting stress gradually released.It reduced the strength and hardness,and improved the elongation of the alloy.The changed of grain boundary types in the molten pool could achieve the columnar-to-equiaxed transition,the preferred orientation weakened,and the texture gradually disappeared.At the same time,the glided and climbed of dislocation could transition from the Low-angle grain boundary to the High-angle grain boundary,and the average orientation angle increased.The intergranular corrosion resistance of the alloy was enhanced due to the increased in the proportion of low（50）-CSL（Coincidence Site Lattice）grain boundaries.Annealing heat treatment was an effective method to improve structure and properties of the alloy.Based on the model designed by Solid Works,AlSi10Mg powder was used as raw material,and the process parameters used in this experiment were used as reference to complete the SLM forming of the“Bing Dwen Dwen”entity.The results showed that after the three-dimensional model is modeled and assembled,the coordination relationship was correct,and there was no static interference inside the assembly.After scaling,slicing and adding supports,the three-dimensional model was transformed into two-dimensional data,which could be directly used in SLM equipment.The entity had a smooth surface,good cleanliness,and accurate dimensional accuracy after removed the support,ground and sandblasted.