Research On Key Technology Of Metal Mirror Modified Surface Polishing

Aluminium mirrors are widely used in aerospace and weaponry applications,but as the performance of optical systems improves,so do the surface roughness of mirrors and other indicators.Currently,single point diamond turning with a nickel-phosphorus modified layer chemically coated on the surface of metal mirrors,combined with subsequent polishing processes to improve the surface shape accuracy and surface quality of the mirror is a common means.However,in the actual high-precision polishing process,it is found that the surface accuracy of the mirror surface is closely related to the polishing environment,polishing medium and polishing force,and improper control is very likely to result in scratches and defects visible to the naked eye,leading to deterioration of surface roughness and affecting the practical application of the mirror.Therefore,it is of great importance to investigate the ultra-precision polishing process of the nickel-phosphorus modified layer of metal mirrors and to form a specific and feasible processing route.Based on a thorough study of the surface properties of the modified layer,the thesis focuses on optimising the magnetorheological polishing fluid configuration as well as the polishing process parameters to form an efficient and high-precision process route by combining ion beam and small abrasive head polishing processes,providing theoretical and experimental support for the processing of high-performance metal reflectors.The main aspects of the thesis work include the following.1.Surface characterisation of nickel-phosphorus modified layers for metal reflectors.From the chemical coating process,the basic material properties of the modified layer were obtained by measuring the properties of hardness,elastic modulus and reflectivity using scanning electron microscopy,nanoindentation and spectral reflectance detection.The presence of bimetallic effects and bonding conditions are investigated for the differences in properties between the modified layer and the base material,providing a research basis for the processing of the modified layer.2.Optimisation of magnetorheological techniques suitable for the processing of nickel-phosphorus modified layers.Based on the surface defects generated during magnetorheological processing,the processing mechanism of scratch generation is analysed and the scratch problem is solved by optimising the polishing abrasive type and processing process parameters.A magnetorheological fluid suitable for the processing of the modified layer was configured and tested for the removal function to verify the processing feasibility.3.A study of the process technology for improving the roughness of the modified layer.The basic principles of the action of the ion beam and CCOS small abrasive head processes on the modified layer are analysed,and a surface quality better than Ra 0.5nm is obtained by optimising the process parameters.Based on the above research,a combined machining process route suitable for processing the modified layer of metal mirrors is proposed.