| Laser 3D printing is an advanced intelligent manufacturing technology,using laser as a heat source,layer upon layer,to achieve from scratch,from small to large parts manufacturing,the utility model has the advantages of wide application of materials,high design of structure,high precision of forming samples,good mechanical properties and short production cycle.Optical Metal Mirror is widely used in the field of space measurement and remote sensing in catadioptric optical system,so its volume,weight,life and optical performance have strict requirements and standards.The traditional manufacture can reduce the weight of the mirror,but the rigidity is sacrificed,and the manufacture cycle is long,which limits the application to a certain extent.By using 3D printing technology,the light-weight fully enclosed Metal Mirror can be formed,which not only satisfies the requirements of light weight and high specific stiffness,but also enhances the mechanical properties of the Mirror and reduces the production cycle.In this study,Selective Laser Melting(SLM)process is used to print AlSi alloy Optical Mirror,and Laser parameters optimization,lattice structure design,polishing and coating are adopted,fast fabrication,light weight optimization design,good optical reflection and processing performance are achieved.The following studies were conducted:(1)The effect of SLM process parameters on the properties of printed AlSi10 Mg Alloy was studied,and the best parameter window region was obtained.First of all,40 AlSi10 Mg single tracks are printed with SLM process under a large range of laser parameters(P: 100 W～ 400 W;V: 330 mm/s ～ 2500 mm/s).The rule of laser single tracks interaction is summarized by optical microscope and single tracks section metallographic characterization,and the best parameter range window is obtained.Secondly,the optimum laser parameters P = 350 W,v =1.6 m/s for AlSi10 Mg under SLM process are obtained by comparing the density,macroscopical morphology and tensile properties of the 3D bulk print with the parameters selected in the single tracks parameter window.(2)The AlSi10 Mg Mirror with lattice function is designed,which realizes the lightweight structure,vertical self-support and surface densification.The results show that the filling structure of hexagon in the vertical direction can not be finished because of the large space between the filling structure and the light weight structure.The internal lattice structure realizes the self-supporting in the vertical direction and the top forming of the mirror.It has the advantages of vibration reduction,large specific surface area,energy absorption and noise reduction,and saves printing materials.Compared with 200 mm in radius and 150 mm in height,the quality of the solid mirror can be reduced by 80 %.After the mirror surface is densified,the tensile property is improved to 490 MPa and the hardness is 130 HV,which can effectively improve the internal defects and prevent the mirror surface from cracking.(3)According to the surface condition of SLM Mirror and the requirement of its optical design,the AlSi10 Mg Mirror printed by laser 3D is post-processed to improve its optical performance and optimize its internal structure.The laser 3D printed AlSi10 Mg Mirror was post-processed to improve its optical performance and optimize its internal structure.Firstly,the polishing effects of chemical polishing,electrolytic polishing and sandblasting were compared and analyzed.The internal lattice structure of the mirror was treated by chemical polishing to effectively remove the metal residue adhered to the surface of the printed part due to the step effect and spheroidization.Secondly,the external surface roughness value of the mirror was reduced to the nanometer level by electrochemical polishing,to reduce the size error in the system assembly.Finally,a silver reflecting layer of about 300 nm thickness was deposited on the polished Mirror by electron beam evaporation,and the reflectivity was over90 % in the wavelength range of 400～1000 nm. |
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