Effects of beam shaping on temperature, pool geometry, and cooling rate in laser powder bed fusion

Abstract

Laser beam shaping is a process of adjusting the intensity profile of the beam to generate an optimal energy distribution at a specific location. In laser powder bed fusion (LPBF), the shape of the laser beam impacts peak temperature, melt pool geometry, and cooling rates, however, a detailed scientific understanding of these effects is lacking. In this research, a 3D transient heat transfer model is implemented to investigate the dependence of temperature fields, melt pool geometry, and cooling rates on six different laser beam shapes: Gaussian, elliptical-Gaussian, top hat, flat top, ring-shaped, and adjustable mode beam. The model results are validated using experimental data for different beam shapes during LPBF of an aluminum alloy, AlSi10Mg. We found that a Gaussian beam, with its concentrated power, results in high peak temperatures and a larger melt pool with slow cooling, whereas an elliptical Gaussian beam produces a wider pool. The top hat and flat top beams distribute power more uniformly, leading to lower peak temperatures and faster cooling, with the flat top beam creating a wider but shallower pool. The ring-shaped beam, spreading energy over a larger area, significantly reduces peak temperature and cooling rate, while the adjustable mode beam with 80 % power in the outer ring exhibits similar temperature fields and pool dimensions to the ring-shaped beam.