Microfracture mechanism of longitudinal torsional ultrasonic-assisted milling of 49Fe-49Co-2V alloy: experiment and MD simulation

Abstract

The 49Fe-49Co-2V soft magnetic alloy faces challenges such as surface fragmentation and poor machining quality during conventional processing, significantly limiting its operational efficiency. Longitudinal torsional ultrasonic-assisted milling (LTUM) has emerged as a promising technique to address these challenges. This research integrates molecular dynamics (MD) simulation and LTUM experiments to systematically investigate the multiscale influence of ultrasonic vibration on the microfracture mechanism of the alloy. The results reveal that ultrasonic vibration suppresses brittle fracture by enhancing plastic deformation and activating dislocation motion, achieving an 84% reduction in the fracture surface length. The introduced ultrasonic energy promotes atomic plastic flow within the cutting zone, with surface atoms exhibiting a maximum displacement of 44 Å, thereby improving the material removal rate. High-frequency ultrasonic impacts facilitate dislocation annihilation, reducing average dislocation density by up to 25%. This mechanism alleviates dislocation pile-up and localized stress concentration, effectively delaying the nucleation and propagation of microcracks. These results provide novel insights into the micro-removal mechanism of the 49Fe-49Co-2V alloy, advancing its potential for high-precision industrial applications.