Towards understanding the surface/subsurface formation mechanism of ultrasonic vibration assisted machining of SiCp/Al composites under different amplitudes

Improving the processing quality of SiCp/Al composites faces significant challenges owing to the pronounced differences in the removal mechanisms of the SiC particles and the Al matrix. Ultrasonic vibration assisted machining (UVAM) is an attractive solution for upgrading the machinability of SiCp/Al composites. However, the impact of different amplitudes on the surface/subsurface formation mechanism has not been systematically investigated. In this study, the evolution of cutting force, surface quality, subsurface damage (SSD) and microstructural deformation under different ultrasonic vibration amplitudes was thoroughly investigated by a series of machining and testing experiments. The reduction proportion of the cutting force is enhanced with the growth of ultrasonic vibration amplitude, and the decrease in cutting force primarily derives from the Al matrix. The variation of surface roughness is governed by the alteration of SiC particle removal pattern under ultrasonic vibration, and a reasonable ultrasonic vibration amplitude facilitates particle fragments rather than fracture. Additionally, the occurrence of SSD depends on the collective effect of the cutting force and the high frequency vibration of the tool. It is worth emphasizing that the small cutting force may not imply the expected surface/subsurface improvement. The minimal surface roughness and SSD depth are achieved when the ultrasonic vibration amplitude is 5 μm. Finally, the residual tensile stress occurs in SiC particles and the grain refinement of Al matrix is observed. This study contributes to the rational selection of ultrasonic vibration amplitude in manufacturing so as to enhance the potential applications of SiCp/Al composites.