Silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al), which possess outstanding mechanical and thermal properties, have become critical materials in advanced fields such as aerospace and automotive electronics. However, the heterogeneous structure formed by a high volume fraction (60%) of SiC particles and the Al matrix tends to induce unique machining defects like particle fracture and matrix tearing, severely restricting their precision applications. Ultrasonic vibration-assisted milling (UAM) provides an innovative technical approach to this issue. Nevertheless, current studies on the tool-workpiece interaction mechanism and parameter optimization of SiCp/Al under axial UAM remain to be further explored. Firstly, a kinematic model for tool-workpiece interaction in axial UAM is established, and the formula for the separation time per cycle between the tool and workpiece is derived, revealing the mechanism by which ultrasonic vibration inhibits heat accumulation and excessive fragmentation of SiC particles by shortening the contact duration. Secondly, a series of single-factor experiments on spindle speed, feed rate, milling depth, and ultrasonic amplitude are conducted. The results show that the surface quality reaches the optimal level when the ultrasonic amplitude is 4 μm: compared with conventional milling (CM), the surface roughness parameters Ra, Rz, Sa, and Sq decrease by 39.24%, 15.06%, 22.00%, and 21.01%, respectively, while the surface fractal dimension decreases by 3.47%. Finally, through orthogonal experiments and range analysis, the optimal machining parameter combination is determined as follows: spindle speed of 9000 r/min, milling depth of 50 μm, feed rate of 30 mm/min, and ultrasonic amplitude of 4 μm. This research delivers a technical foundation for enhancing the machining quality of SiCp/Al composites through UAM.
