A Study Of Factors Affecting Surface Roughness In Ultra-precision Turning Of 6061 Aluminum Alloy Based On Aging-characteristics

Diamond turning being a kind of ultra-precision machining technology,can directly produce a high-quality surface without the need for the post polishing.As well known,diamond turning enables sub-micron form accuracy and nanometric surface roughness manufacturing.With the wider and wider applications of ultra-precision machined components,the requirements on the achieved quality of the surface are getting higher and higher.Surface roughness is a key parameter for evaluating surface quality,but it is affected by many factors in ultra-precision machining.However,in the study of material properties on surface roughness in ultra-precision machining,more attention was paid to study the effect of material deformations and grain size,crystal orientation,etc.Aluminu m alloy 6061(Al6061)is a heat-treatable Al-Mg-Si aluminum alloy with the main alloying elements of Fe,Si,Mg.Al6061 is widely used in automobile manufacturing and aerospace industry because of its advantages of light weight,moderate strength,good formability and corrosion resistance.However,there exstes precipitates in the materials which affects the achieved surface quality in ultra-precision machining.This paper mainly studies the aging characteristics of Al6061,and the effect of the precipitation on the surface quality in ultra-precision turning.A new surface roughness prediction model for Al6061 in ultra-precision turning is established,and the experiments were designed to verify the validity of the model.The main research contents are as follows:(1)The aging characteristics of Al6061 were studied by experiment and the generation principle of precipitation was analyzed.The experimental results show that the precipitation that affect the surface quality in ultra-precision turning are?,?-Al Fe Si and Mg₂Si,respectively.(2)By studying the surface formation of Al6061 in single-point diamond turning,the effect of precipitation on surface generation and cutting force was analyzed.Based on the experimental study,the surface roughness of Al6061 caused by the precipitation was quantitatively analyzed.The experimental results show that the precipitation will produce protrusions,pits and scratches on the ultra-precision turning surface,its formation is related to the relative position of the tool and the precipitation and the size of precipitation also contributes to it.It also causes the cutting force to fluctuate in the cutting direction.Especially,the surface roughness caused by the precipitation is directly proportional to the number of the precipitations.Therefore,the aging treatment can contribute to making effectively control the precipitations and improving the surface quality in ultra-precision machining.(3)Based on the existing prediction model of ultra-precision turning surface roughness,a new surface roughness prediction model is establish.A new model take the effect of precipitation on surface roughness into account,the experimental verification is carried out.The experimental results prove that the surface roughness predicted by the new model is closer to the actual machining surface roughness,and the prediction error is within 9.46%.