In order to study the effect of the ultrasonic impact on the surface integrity of titanium alloy

the mechanism of ultrasonic impact is analyzed and TC4 titanium alloy is selected to carry out ultrasonic impact experiments on different machined surfaces. The roughness

hardness

microhardness

residual stress and plastic deformation layer depth were measured and analyzed before and after ultrasonic impact. The results show that ultrasonic impact strengthening can reduce the surface roughness to Ra = 0.15 μm and generate a large residual compressive stress on the surface of the specimens

and the machined surface condition before strengthening has no significant effect on the final impact surface roughness and residual stress. In addition

the ultrasonic impact strengthening sample has a higher surface microhardness

which is 18% higher than that of the untreated sample

and the depth of the hardened layer reaches 130 μm. Ultrasonic impact strengthening changes the metallographic structure on the surface of the workpiece. Using SEM

it is found that the α phase is refined and the surface grains are directionally deformed

which is the main reason for the increase of the surface hardness. Comparing with the other strengthening processes

ultrasonic impact can reduce the roughness of the machined surface and improve its residual compressive stress and hardness. At the same time

the equipment cost is low and the versatility is strong

which is of positive significance for improving the surface quality and fatigue resistance of the workpiece.