In this study, NiAl bronze (NAB) alloys are processed using an ultrasonic vibration-assisted milling (UVAM) surface engineering technique. The strengthening mechanisms at different cutting speeds are analysed through well-established models and experiments. The increase in cutting speed produced decrements of 29.5%, 26.6%, and 5.6% in the friction torques, accumulated dissipated energy, and worn surface area, respectively. The microhardness gradually increased by 11%, which helped improve the fretting wear performance. Grain refinement, precipitation, and dislocation strengthening were the main mechanisms. Grain refinement (∆σHP) had the greatest contribution to performance, followed by precipitation (∆σor) and dislocation (∆σd). Nanotwin strengthening was observed at a cutting speed of 150 m/min. Martensite nanotwins may nucleate at the grain boundary and grow toward the grain interior.