Numerical investigation on serrated chip formation during high-speed milling of Ti-6Al-4V alloy

Abstract

Due to several inherent properties, Ti-6Al-4V alloy is a kind of typical difficult-to-machine material, especially during high-speed milling processes. The combined action of translation and rotation motion, as well as the short and variable undeformed chip thickness generation, make the milling process different from the turning process. Hence, it is essential to investigate the thermo-mechanical effect on serrated chip formation mechanism during the high-speed milling of Ti-6Al-4V alloy. The present paper investigates numerical methodology (i.e., the combined action of material constitutive with an energy-based ductile failure mechanism) for serrated chip formation in high-speed milling of Ti-6Al-4V alloy. First, a simplified 2D milling model was adopted based on the J-C constitutive equation combined with the energy density-based failure material model. Secondly, the proposed model was corroborated through experimentally obtained results. A good correlation was found between the numerically adopted model and experimentally obtained results. Thirdly, the physical phenomenon of the serrated chip formation and the effect of friction coefficient on shear stress is highlighted and discussed. Finally, the chip back surface's microstructural changes and phase transformation were investigated. The present investigation is beneficial to well understanding the serrated chips formation during high-speed milling of Ti-6Al-4V alloy as well as to optimizing process parameters and maintaining desirable machined surface integrity.