Material removal mechanism in rotary ultrasonic machining of high-volume fraction SiCp/Al composites

High-volume fraction silicon carbide-reinforced aluminum matrix (SiCp/Al) composites are widely used in many industrial fields due to their excellent material properties. However, these composites are regarded as one of the most difficult-to-machine materials, owing to the presence of many hard and brittle SiC reinforcements. Rotary ultrasonic machining (RUM) is an effective processing method for SiCp/Al composites. The material removal mechanism in RUM of SiCp/Al composites was investigated by comparing the deformation characteristics of the composites in ultrasonic vibration-assisted scratch (UVAS) tests and conventional scratch (CS) tests which were performed on a rotary ultrasonic machine. The influence of ultrasonic vibration on the machining process was analyzed. Furthermore, the morphologies of the scratching surfaces, scratching forces, and material removal process were evaluated in detail. The theoretical and experimental results revealed that ultrasonic vibration changes the interaction between the cutting tool and the workpiece. The vibration enhanced the Al matrix and facilitated SiC reinforcements removal by increasing the cracks in them. Therefore, the scratching forces in UVAS were smaller and more stable than those in CS. The coefficient of friction (COF) was also smaller than that of CS and hence, the adhesion effect of Al matrix during the scratching process was weakened. This study shows that the removal mode of SiC reinforcements plays a decisive role in the formation of the machined surface. These results can serve as a guide for selecting appropriate processing parameters to obtain improved machining quality of SiCp/Al composites.