Research On Process,Microstructures And Properties Of AlSi10Mg Aluminum Alloy Prepared By Laser Melting Deposition

With the development of aerospace technology,Al alloy structural parts evolve toward the large-scale,integrated,complex shape,thin-walled,high-precision.Laser melting deposition technology is a new metal addictive manufacturing technology,and low cost,high utilization rate,short processing cycle and other technical advantages make it have a wide range of applications.However,Al alloy itself has a low absorption rate of laser,large thermal conductivity,bad fluidity,and these bring laser melting deposition forming process a great challenge.In this paper,the process characteristics and principle of laser melting deposition technology were expounded.The feasibility,forming process,microstructures and properties of laser melting deposited AlSi10Mg alloy were studied.The main work is as follows:?1?The feasibility of laser melting deposited of AlSi10Mg alloy was verified.Deposited samples with compact structure of rapid solidification can be successfully prepared by laser melting deposition technique,such as strip deposit,thin wall box and so on.?2?The influence of laser power P and scanning velocity Vs on the morphology of single track of laser melting deposition was investigated.In a certain process,the width and depth increase with the increase of P,and decrease with the increase of Vs.It is found that the heat accumulation of the substrate during the deposition has a great effect on the deposition morphology.?3?A new method for characterizing the thermal accumulation of aluminum alloy by laser melting deposition was proposed.The matrix heat accumulation factor?X_R?is defined to represent the matrix heat accumulation and a simplified mathematical model was established.With the increase of heat accumulation,the width and depth become larger.The contact angle ? and the dilution ? are linearly related to X_R.The contact angle ? decreases with the increase of X_R,and the dilution ?increases with the increase of X_R.?4?The phase composition and microstructural evolution of AlSi10Mg alloy by laser melting deposition were analyzed.AlSi10Mg samples were composed of ?-Al phase,eutectic Si and Mg₂Si strengthening phase.The microstructures are continuous columnar crystal structures with continuous epitaxial growth,and gradually change into equiaxed grains at the top of the uppermost sedimentary layer.The yield strength of AlSi10Mg reaches 183.65 MPa and the microhardness reaches 100 ¹30HV.?5?The effects of heat treatment on the microstructures and properties of AlSi10Mg alloy were investigated.The process,"solution+aging",can effectively improve the yield strength of the AlSi10Mg alloy.The coralline branches of the Si phase in the sample after the heat treatment are almost disappeared,and the eutectic Si phase exists in the dispersed circular granularity.The yield strength of the specimen reaches 237.61MPa.