Sen Yin, Xinran Liu, Zhicheng Xu, Yanan Pan, Zhigang Dong, Suet To
Controlled nuclear fusion represents the ultimate solution to humanity's energy challenges, and tungsten alloys are indispensable in nuclear fusion applications due to their exceptional radiation resistance. However, the hard-brittle tungsten particles coupled with the soft-viscous nickel-iron phase presents significant challenges during machining. Energy-fields assisted machining is the primary technique for ultra-precision machining for tungsten alloys, but research on the surface formation mechanisms of ultrasonic vibration assisted grinding (UVAG) for tungsten alloys remains insufficiently explored. Therefore, based on FE simulation and scratch experiments, this study investigated the material removal mechanism and microstructure evolution of tungsten alloys. The results demonstrate that ultrasonic vibration can weaken the ploughing effect, resulting in higher material removal rate, emerging ductile material removal, but this effect weakened with the increase of scratch depth. In addition, ultrasonic vibration elevates the plastic strain rate by an order of magnitude, which significantly influences the microstructure through dynamic stress accumulation: the thickness of the grain refinement layer decreases from 1.5 μm to 0.7 μm, and tungsten particles initially 2 μm in width are refined to less than 1 μm. Concurrently, ultrasonic vibration expands the region affected by elevated dislocation density. At equivalent depths, the dislocation density increases by a factor of 3-5 compared to the base. Leveraging these findings, the experimental parameters for UVAG are optimized, realizing the ductile domain grinding for tungsten alloys, leading to a significant enhancement in surface quality. This study establishes a fundamental mechanistic framework for optimizing UVAG process of tungsten alloys, thereby contributing to improved processing quality and service performance of key nuclear fusion device components.