Abstract: To study the intrinsic mechanism by which elliptical ultrasonic vibration milling (EUVM) enhances the subsurface mechanical properties of GH4169, comparative experiments are conducted under both EUVM and conventional milling (CM). The cutting characteristics are investigated under varying cutting parameters. Subsurface microstructural changes are analyzed using material characterization techniques, and the effect of machining conditions on subsurface mechanical behavior is revealed. Experimental results indicate that the cutting force of EUVM, under wet cutting, is overall higher than that of CM, up to 16.76%. Similar force peak positions suggest that the determining factors affecting the cutting force are the cutting parameters rather than the vibration parameters. EUVM produces uniformly arranged wavy micro-textures on the machined surface, resulting in increased surface roughness, up to 0.781 μm. An increased number of low-angle grain boundaries and higher dislocation densities in the subsurface grains are observed, attributed to the enhanced dislocation motion and interaction induced by the vibrational and velocity effects of EUVM. Compared with CM, EUVM-induced microstructural evolution contributes to a maximum increase of 48.4% in work hardening and 76.98% in compressive residual stress. However, the gap in dislocation density between EUVM and CM is reduced at higher process levels, primarily due to the weakening of ultrasonic vibration effects at elevated cutting speeds. The results provide valuable guidance and reference for the fatigue-resistant manufacturing of GH4169.

Key words: elliptical ultrasonic vibration milling, GH4169, cutting characteristic, microstructure, mechanical properties