Study On The Effect Of Ultrasonic Vibration Rolling On The Surface Quality Of TC4 Alloy

TC4 titanium alloy has been widely used in the fields of aerospace,shipbuilding,chemical industry and medical equipment due to its low density,high specific strength,high temperature resistance,high corrosion resistance,shape memory function and excellent biocompatibility.Because the surface of TC4 titanium alloy is prone to oxidation pollution,and titanium alloy parts are also prone to fretting wear,friction wear,crevice corrosion and other defects due to their low surface hardness during use,these defects can lead to security risks in the application process of titanium alloy parts and increase the use cost and other problems.As a metal surface treatment technology,ultrasonic vibration rolling processing technology is widely used in various fields of production and is an ideal surface strengthening technology.In this paper,the ultrasonic vibration rolling processing technology was applied to the surface treatment of TC4 titanium alloy.The surface roughness,microhardness and residual stress were taken as the evaluation indexes of TC4 titanium alloy surface quality.The influences of machining parameters such as spindle speed,feed speed,static pressure and processing times on the surface quality were explored.The results show that the ultrasonic vibration rolling process can reduce the surface roughness of TC4 titanium alloy,improve the microhardness and introduce the residual compressive stress.And the appropriate spindle speed,feed speed and processing times will greatly reduce the surface roughness.Within a certain range,the surface roughness will decrease with the increase of static pressure.However,the spindle speed has little influence on the microhardness of the material surface.The microhardness decreases with the increase of feed speed and increases with the increase of static pressure and machining times.The value of the residual stress on the material surface decreases with the increase of the feed speed and increases with the increase of the static pressure and the number of machining times,and there is no obvious relationship between the value of the residual stress on the material surface and the spindle speed.After the ultrasonic vibration rolling processing of TC4 titanium alloy,its surface becomes smooth and flat,and the micro irregularity is basically eliminated.The average surface roughness Ra drops from 0.97 ?m before processing to 0.17?m,and other roughness parameters all have a significant decrease.On the surface of TC4 titanium alloy,a severe plastic deformation layer with a thickness of about50 ?m was generated.The grain structure in this zone was significantly refined.With the increase of the distance from the surface,the grain structure of the material gradually increased and the plastic deformation gradually decreased.The XRD pattern of TC4 titanium alloy surface after the process was significantly weakened and widened,and the diffraction Angle was shifted to a higher Angle,indicating that the process could effectively refine the surface grains of TC4 titanium alloy and introduce residual compressive stress on the material surface.The surface microhardness of TC4 titanium alloy increased from 319 HV to421HV after processing by this process.Within the depth range of 0-140 fastm away from the surface layer,the microhardness gradually decreased with the increase of the depth,indicating that an effective hardening layer with a thickness of about 140 ?m was formed on the surface layer of the alloy after processing by this process.The maximum value of residual compressive stress on the surface of TC4 titanium alloy can reach-967 mpa after processing by this process.The value of residual compressive stress increases with the increase of the distance to the surface within a depth of about 0-50 ?m away from the surface,and decreases with the increase of the depth when the depth is greater than 50 ?m away from the surface.