Study On The Surface Quality Of Selective Laser Melting AlSi10Mg

Selective Laser Melting(SLM)is one of the most promising technologies in metal additive manufacturing.However,the limited surface quality of the SLM technology impedes its development and application.In this thesis,the influence of the defocus amount,the process parameters and remelting process parameters,such as laser power,scanning velocity,scanning space on the side surface quality and top surface quality of SLMed AlSi10 Mg sample was studied systematically.Furthermore,the method for improving the surface quality of SLMed AlSi10 Mg sample was also studied.The main research content and results of this thesis are as follows:(1)The effects of contour process parameters such as cotour laser power,contour scanning velocity,and scanning strategy on the side surface quality of SLMed AlSi10 Mg samples were studied.It was found that adding a regular uniform contour track can improve the side surface quality significantly.Two scanning strategies: entity first then contour and contour first then entity,can obtain high side surface quality.The smaller the amount of defocus is,that is,the closer to the focal position,the more regular and uniform the contour track of the shaped sample is,and the higher the side surface quality is.(2)The effects of process parameters on the top surface quality and density of the fabricated samples were studied.The research results show that the quality of the top surface is also closely related to the surface quality of the forming entity track.Only a regular and uniform entity track with a suitable track width and the amount of overlap can obtain a high top surface quality.The relative density and the surface roughness of the fabricated sample are closely related,and their relationship with the process parameters is almost opposite.Using appropriate process parameters can achieve both high top surface quality and high relative density.The optimal process parameters of thin-walled parts with different wall thicknesses are different.The laser line energy density increases from 0.14J/mm at a wall thickness of 0.1mm to 0.30J/mm at a wall thickness of 2mm.(3)The influence of the defocusing amount on the quality of the top and side surfaces is studied.The results show that when the amount of defocus is large,the track width-todepth ratio is large,and the best top surface quality can be obtained,but the side surface quality is very poor due to the uneven and irregular track.When the amount of defocus is 0mm,that is,the focal point,due to the uniform track,the best side surface quality can be obtained,but the aspect ratio is small,and the top surface quality is very poor.When the defocus amount is moderate(±3.5mm),good top surface quality and side surface quality can be obtained simultaneously.Within the range of the experimental parameters,the optimal defocus amount is-3.5mm or +3.5mm.(4)The effect of remelting on the top surface quality of SLM formed AlSi10 Mg samples was studied.It was found that when the top surface roughness is large,the top surface roughness Ra and Rz of the SLMed AlSi10 Mg sample decreases with the increase of the remelting laser power and scanning speed,and increases first and then decreases with the increase of the remelting scanning space.As the times of remelting increases first decreases and then increases,and is not closely related to the remelting phase angle.Appropriate remelting process parameters can remelt and solidify the rough top surface,and the track is stable and uniform,and the quality of the top surface is improved.But compared with the optimal top surface quality without remelting,remelting did not improve the top surface quality of the sample significantly.