Study On Spectral Scattering Characteristics Of Aluminum Alloy Surface With Quasi-periodic Microstructure

At present,due to the limited types of processing materials,high requirements for equipment and environment,long processing time,high price and other factors,the industrialization of microstructure functional surface special machining technology is limited.Quasi-periodic microstructure can be formed on metal surface by adjusting machining and surface treatment.By changing the spectral radiation characteristic parameters of metal surface in this way is an effective way to explore the regulation and control of surface spectral radiation characteristics with low cost and large-scale application.Therefore,the spectral scattering characteristics of quasiperiodic microstructure aluminum alloy surface formed by machining and surface treatment will be studied in this paper.The bidirectional reflection distribution function(BRDF)can reflect the spatial distribution of reflection and scattering intensity on the surface of objects,and has an important application in the study of radiation characteristics of metal surfaces.In this paper,two groups of samples were processed by flat grinding and flat milling,and one of them was blackened.The surface microstructure characteristic dimensions of the two groups were characterized by optical digital microscope,and the selfdesigned BRDF test bench was corrected,so that the BRDF measurement error was less than 5%,and the BRDF,on the surface of aluminum alloy with periodic microstructure was measured.The effects of incident angle,material,roughness and incident radiation wavelength on the distribution characteristics of scattered radiation in the incident plane are studied,and the control means of scattering characteristics of aluminum alloy surface are explored.Based on the five-parameter semi-empirical model,combined with the results of BRDF experimental measurement of quasi-periodic microstructure aluminum alloy surface,taking the standard mean square error as the objective function,the undetermined parameters of BRDF model of flat grinding,flat milling and blackening surface are inversed by genetic algorithm,and the errors are all less than 10%.On the one hand,it enriches the BRDF database of quasi-periodic microstructure aluminum alloy surface,on the other hand,it can provide reference for related engineering applications.In addition,because the polarization bidirectional reflection distribution function(p BRDF)contains more information of polarization scattering characteristics,through the upgrading of the existing experimental bench,the measurement function of sample Mueller matrix and polarization BRDF is realized,and the polarization BRDF of quasi-periodic microstructure aluminum alloy surface blackened by 5A06 flat milling is measured and analyzed.Through the above research,it can be concluded that the quasi-periodic microstructure can have an obvious influence on the surface scattering characteristics of aluminum alloy,and compared with the flat grinding sample,flat milling can change the spatial distribution and spectral distribution of aluminum alloy surface scattering intensity.when the size of quasi-periodic microstructure is in the range of100 ～ 400 μ m,the scattering intensity in the reflection direction of flat milling sample mirror can be reduced by 54% and 75%.By blackening the flat milling sample,the scattering intensity can be reduced by more than 50% without changing its spectral distribution.At 1064 nm wavelength,the blackened sample of 5A06 flat milling has strong depolarization ability in the mirror reflection direction,and its polarization scattering property has strong anisotropy.