Surface integrity and subsurface microstructure evolution induced by ultrasonic elliptical vibration cutting of CoCrFeNiAl0.5 high-entropy alloy

• Ultrasonic Elliptical Vibration Cutting significantly improves the surface quality of CoCrFeNiAl 0.5 High-entropy alloy, reducing surface roughness to 14 nm (a 48% decrease) and flank tool wear by 95% under identical cutting parameters. • While conventional cutting causes severe adhesive wear on the rake face and abrasive wear on the flank face, Ultrasonic Elliptical Vibration Cutting alters the wear progression through intermittent cutting, maintaining minimal tool wear. • Ultrasonic Elliptical Vibration Cutting induces grain refinement and a homogeneous subsurface structure, increasing grain interior hardness by 150% and enhancing mechanical uniformity between grains and boundaries. • Microscopic analysis reveals a graded subsurface architecture—comprising an amorphous layer, stacking faults, and precipitates—that synergistically strengthens surface properties, offering a novel approach for precision machining of High-entropy alloy. High-entropy alloys (HEAs) are promising candidates for high-end aerospace and energy applications due to their exceptional high-temperature strength and corrosion resistance derived from the multi-principal element effect. However, the ultra-precision machining of HEAs remains a significant challenge, as conventional methods like single-point diamond turning (SPDT) suffer from rapid tool wear and poor surface quality. To address this gap, this study employs ultrasonic elliptical vibration cutting (UEVC) to improve the machinability of the CoCrFeNiAl 0.5 HEA. The results demonstrate that, under identical cutting parameters, UEVC reduces surface roughness by nearly half compared to conventional cutting (CC) and decreases flank tool wear to approximately 5% of that in CC, while also effectively retarding the progression of wear. Nanoindentation tests indicate that UEVC increases the hardness of grain interiors by a factor of 2.5 and significantly enhances the mechanical homogeneity of the surface. Moreover, UEVC produces a graded subsurface architecture composed of an amorphous layer, high-density stacking faults, and nano-precipitates, which work synergistically to improve the overall surface performance. In conclusion, this work provides an effective approach for high-quality, low-damage ultra-precision machining of HEAs, establishing UEVC as a viable strategy for manufacturing HEA components that require demanding surface integrity.