Numerical and experimental investigation on pulsed nanosecond laser ablation processing of aluminum alloy

Abstract

The laser ablation of aluminum alloy 6061 was studied both experimentally and by computational modeling in this work. Six variations of the number of pulses of irradiation (1, 5, 10, 20, 50, and 100 pulses) combined with four different laser fluence (2.0 J/cm2, 1.5 J/cm2, 1.0 J/cm2, and 0.5 J/cm2) were chosen to study the effect of heat input and laser action time on microstructural changes and the generation of particulate pollutants. Laser fluence and the number of pulses of laser irradiation were found to have a direct influence on thermal diffusion and the ablation depth of aluminum alloy 6061. At a relatively high laser fluence (2 J/cm2) and with the application of 10 pulses of irradiation, ablation cracks were observed on the surface of aluminum alloy 6061 and the production of pollutant particles increased according to a particle counter. Maintaining the laser fluence at 0.5 J/cm2 while increasing the number of pulses of irradiation to 50 also enhanced the depth of thermal diffusion while laser ablation continued to occur. The occurrence of vaporization in the surface region was influenced largely by laser fluence and the number of pulses of irradiation, as evident from the simulation and from experimental results. The single laser pulse duration was 6 ns and the repetition rate was 1 s−1. This article provides a novelty numerical model which could reveal the metal alloys' evapotation at a high-fluence nanosecond laser ablation. A 3D computational model was used to predict the temperature variation upon laser irradiation in a solid material over time. The results of the model (thermal diffusion versus laser ablation) agreed well with the experimental results.