| Due to the advantages of low density,high specific strength and high specific stiffness,magnesium alloy has a wide application prospect in the transportation industry as a light material.At the same time,magnesium alloy has good biocompatibility,making it a potential biodegradable material for the medical industry.The surface integrity of mechanical parts has an important influence on their performance and function.But the poor surface integrity of magnesium alloy limits its wide application in transportation and medical industry.The surface integrity of workpiece can be effectively improved by different machining cooling methods and technological parameters.In this paper,the influence of cutting parameters on the surface roughness,microstructure,machining hardening and residual stress is studied by using the processing method of liquid nitrogen low-temperature cooling,which provides a theoretical basis for improving the surface integrity of magnesium alloy by liquid nitrogen lowtemperature cooling and changing the processing parameters,and improves its service performance.The main research contents of this paper are as follows:1.The detection and analysis of low-temperature liquid nitrogen cooled turning magnesium alloy samples were carried out by laser confocal microscopy.The influences of different cutting parameters(cutting speed,feed)on surface roughness are studied and the reasons are analyzed.The reasons for the influence of cutting speed and feed rate on the surface roughness are explained.Based on the observation and analysis of the surface topography of different cutting samples,the influence mechanism of the tool material and the radius of the tip arc on the surface roughness was studied.At the same time,the types and causes of surface defects were observed and analyzed.2.Studied the surface properties of processed samples,and studied the influence of cutting parameters(cutting speed and feed)under liquid nitrogen cooling on the plastic deformation of microstructure and surface machining hardening;The microstructure of the surface layer of low-temperature turning specimen was observed by metallographic microscopy,and the influence mechanism of cutting parameters on grain refinement and surface plastic deformation was elucided by comparing the thickness of plastic deformation layer.The surface hardness was measured by vickers hardness tester and the influence of cutting parameters on the degree of machining hardening was studied.3.The simulation study on the surface residual stress of low-temperature turning magnesium alloy was carried out,and the influence law of different cutting parameters on the residual stress was analyzed.The residual stress of machined surface is measured by X-ray method.The accuracy of the experimental results and the output of the simulation model is verified.The trend of influence of cutting parameters on residual stress is obtained. |
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