Selective Laser Melting AlSi10Mg And Its Composite Structure And Performance Study

AlSi10Mg is a kind of casting aluminum alloy,because of its good casting performance and lightweight characteristics,it is widely used in shipbuilding,aerospace,automobile manufacturing and other industries.Aluminum matrix composites are polyphase materials whose strength and extensibility are improved by introducing a second phase into the aluminum matrix.Compared with traditional ceramics,zirconia ceramics have higher hardness,fracture toughness and corrosion resistance.Selective Laser Melting（SLM）has strong material adaptability,and its advantage is that it can overcome the troubles caused by traditional manufacturing of complex parts,and it can form almost full-density metal parts with good mechanical properties.AlSi10Mg and its composite materials are formed by SLM.It is of great significance to enhance its mechanical properties.In this paper,the effects of SLM forming process parameters,annealing under different conditions on the microstructure,phase structure and mechanical properties of AlSi10Mg were studied,and high density AlSi10Mg SLM forming samples were obtained.ZrO₂ ceramic particles were used as reinforcement material and AlSi10Mg alloy powder was mechanically mixed.ZrO₂/AlSi10Mg composite alloy was prepared by SLM.The effects of ZrO₂ particles on the microstructure,phase distribution and mechanical properties of the formed composite alloy were investigated.Compared with AlSi10Mg,the elongation of ZrO₂/AlSi10Mg composite alloy is greatly improved.A series of annealing treatments are carried out on AlSi10Mg alloy and ZrO₂/AlSi10Mg composite alloy.The effects of annealing on microstructure and morphology of samples are analyzed,and the changes of phase distribution before and after annealing are compared.The changes of mechanical properties of samples before and after annealing were also discussed.The results are as follows:（1）The variation of process parameters has a great influence on the forming quality and mechanical properties of AlSi10Mg sample formed by SLM.In this paper,the combination of process parameters shows that the density of the sample can reach 99.82%when the laser power is 350W,the scanning distance is 0.13 mm,the scanning speed is 1200 mm/s and the layer thickness is 30μm.ZrO₂ particles in ZrO₂/AlSi10Mg composites formed by SLM are distributed uniformly and have good interfacial bonding with AlSi10Mg matrix.The addition of ZrO₂ particles plays an important role in grain refinement of ZrO₂/AlSi10Mg composites.The addition of ZrO₂ particles produces a napping effect at the grain boundary.Thus,the grain size is refined to achieve fine grain strengthening.（2）The texture coefficient（TC）of Al（200）crystal plane of AlSi10Mg sample before and after annealing is higher than that of other crystal planes,which is the preferred orientation ofα-Al matrix of AlSi10Mg alloy formed by SLM.After annealing at 100～200℃for 1 h,the eutectic Si of AlSi10Mg samples formed by SLM is still in continuous network distribution,and the hardness decreases from 131.5HV to 117.5 HV.After annealing at 300～400℃for 1 h,the fracture and spheroidization of Si in the alloy samples occur and some coalesce occurs in the Al matrix,and the microhardness decreases to 55.4 HV.（3）The composite alloy is composed ofα-Al phase and eutectic Si before and after heat treatment,and the agglomeration of Si particles gradually increases with the increase of annealing temperature.The tensile strength of ZrO₂/AlSi10Mg deposition reaches 420.52 MPa,which is 93.71 MPa higher than that of the substrate.The elongation reached9.51%,an increase of 77.58%.With the increase of annealing temperature and holding time,the size and number of dimples on tensile fracture surface showed an increasing trend,and the fracture mode was ductile fracture.Within a certain temperature range,the elongation of the composites increases with the increase of annealing temperature,while the tensile strength decreases.After annealing at 400℃/2h,the elongation reaches 22.65%and the tensile strength decreases to 215.28MPa.