Thermo-flow modeling of geometry evolution considering the velocity flow fields during pulsed-laser processing

Abstract

This paper evaluates the effectiveness of laser beam micromachining (LBMM) by analyzing the characteristics of the molten metal flow field during the development of micro-features on metallic surfaces. It establishes a foundation for understanding defects such as recast layer thickness, microcracks, and bulges arising from this flow and offers insights on controlling these issues. Effectively managing and optimizing these factors can help reduce the time and costs associated with the process. A transient coupled thermo-flow numerical model has been developed to study the hydrodynamic performance of bio-materials like titanium alloy (Ti-6Al-4V), which is widely used in biomedical and aerospace industries. The model considers the effect of the driving forces, viz., viscous force, thermocapillary force, and recoil pressure, which plays an essential role in geometry evolution. The mechanism of geometry evolution and molten metal flow behavior is analyzed as the pulse number increases, and the effect of pulse energy on geometry evolution is also predicted. The developed model predicted a depth of around 35─40 μm at the end of the 10th pulse. The results obtained from the developed model were compared with the published results, which verified the model's validity. Overall, the developed thermo-flow model and results obtained provided insights into the molten pool formation and geometry evolution during laser processing of Ti-6Al-4V.