| Silicon carbide particle reinforced aluminum matrix(SiC_p/Al)composite material,as a new lightweight material,has the advantages of excellent performance and low cost,so that it has been widely used in aviation,aerospace and military fields.However,traditional manufacturing methods can not meet the requirements of complex shape aluminum matrix composites.Selective Laser Melting(SLM)as a new manufacturing process in the world,has the advantage that it can process unconventional structural parts which can not be processed by traditional manufacturing methods or difficult to be processed;moreover,due to the melting of all metal powders during SLM forming,the density of the parts is relatively high;in addition,the fast cooling rate can greatly refine the structure of the material and significantly improve its mechanical properties,which is expected to be solved the difficulties encountered in traditional manufacturing methods.In this paper,SiC_p/AlSi10Mg composite samples have been successfully prepared by the SLM process.Taking the SiC_p/AlSi10Mg samples as the object,the relationship between powder and powder fluidity,the defect formation mechanism,the relationship between microstructure and mechanical properties,and the control method of heat treatment in SLM forming process have been systematically studied,and high-performance SLM composite has been realized.The main conclusions are as follows:The influence of powder characteristics of SiC particles and AlSi10Mg alloy powder on powder fluidity is studied,and the problem that powder hard dropping due to poor fluidity is solved.It is found that the fluidity of powder is determined by the shape and the distribution of particle size.The more irregular the shape of powder and the more fine powder content,the lower the fluidity of powder.In order to improve the fluidity of powder,the round shape and medium particle size should be selected.The fluidity of powder can also be improved by means of vacuum pumping.The influence of the parameters(scanning speed and scanning distance)of selective laser melting of SiC_p/AlSi10Mg composite on the defects of the formed parts is studied,and a set of parameters for densification forming is obtained.It is found that the densitometry decreases with the increase of scanning speed and increases first and then decreases with the increase of scanning distance.Based on the analysis of the causes of the defects,the criterion of SiC_p/AlSi10Mg crack was obtained,which laid the foundation for the process optimization of SiC_p/AlSi10Mg composites.The optimized process parameters are:laser power 280W,scanning speed 1000mm/s,scanning distance 0.14mm,layer thickness 30?m.SiC_p/AlSi10Mg composite was prepared by optimized process parameters,and the influence of the volume fraction of SiC reinforced particles on the microstructure and mechanical properties of SiC_p/AlSi10Mg forming samples was studied.It is found that Al4SiC4 phase can be produced by increasing the volume fraction of SiC particles.With the increase of the volume fraction of SiC particles,the Brinell hardness and friction and wear properties will be improved.However,the volume fraction of SiC reinforced particles has a theoretical limit.If the theoretical limit is exceeded,the microstructure distribution will become uneven,resulting in defects.The effect of annealing process on the microstructure and mechanical properties of SiC_p/AlSi10Mg samples form SLM were studied.It is found that with the increase of annealing temperature,the diffusion of Si atom in supersaturated solid solution in?-Al matrix is promoted,and Si atom begins to precipitate to white dispersion particles;the eutectic structure of Al-Si gradually begins to dissolve and disappear,the shape changes from strip to round,and from the original aggregation state to dispersion.The Brinell hardness of the samples increased first and then decreased,and the friction and wear properties also increased first and then decreased. |
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