Electromagnetic, thermal and hydrodynamic investigation of LIPSS formation on Ti6Al4V induced by femtosecond laser processing

Laser-induced periodic surface structures (LIPSS) have garnered significant attention due to their applications across various fields. Nevertheless, the formation mechanisms and fabrication methods of LIPSS on metal and alloy surfaces remain a focus of scientific investigation. In this study, the titanium alloy Ti6Al4V is selected as the target material. A multiphysics model is developed to examine the process ranging from femtosecond laser irradiation to LIPSS formation on Ti6Al4V. The roles of electromagnetic, thermal and hydrodynamic fields in the formation process, corresponding to laser absorption, energy transport and material transport processes, are explored. The mechanism behind LIPSS formation is elucidated. Numerical simulations of surface morphology after multiple laser pulses align well with experimental observations. It is found that the thermal and hydrodynamic fields play an important role in the formation of rough surface, while the effect of electromagnetic field leads to the formation of periodic structures. Furthermore, a line scanning of the laser focus scenario is integrated into the developed multiphysics model, by varying the equivalent pulse numbers at different scanning speeds. The simulation results of line scanning are consistent with the experimental results. This work provides a theoretical basis for the LIPSS formation on Ti6Al4V and informative assistance in processing parameters exploration.