36 - Comparative study of gaussian, top-hat and donut laser distribution for powder bed fusion additive manufacturing of AlSi10Mg alloy.
Abstract
Laser beam shaping is the subject of a growing interest for laser powder bed fusion process (L-PBF) as circular gaussian beam induces instabilities (ejectas, roughness, keyhole porosities). The high peak power density (W/m²) in the center of the melt pool compared to the low intensity on the edges creates high local temperatures and thermal gradients. Using modified intensity distributions may lead to a better control over the temperature distribution, melt pool dynamics and solidification parameters. The AlSi10Mg alloy is a challenging one to process due to its high reflectivity, high conduction and oxydation sensitivity. With this alloy, the donut beam shape creates larger but shallower melt pools which tend to foster process stability while reaching high density. On other alloys, the litterature indicates that beam shaping shows the same stabilisation tendency with less deep keyhole as well as different solidification mode. Circular top-hat and donuts prove to reduce the denudation area along the melted lines while elliptical beam reduces texture by triggering more equiaxial growth. In the current study, AlSi10Mg alloy is processed with gaussian, top-hat and donut laser beams with the use of a small home-made LPBF system, and diffractive optical elements (DOEs) to obtain the aforementions top-hat and donut beams from the incident Gaussian shape. First, laser beam profiles are characterized with a beam analyzer and used as input data of a 3D quasi-stationnary FE thermal modeling. Second, single tracks and small cubes are built under argon gas flow with the three beam shapes considering a range of energy conditions (P, V) in order to highlight the specific effects on the melt pool geometry and stability (spatters), and on metallurgical properties (porosity rate, microstructure size, texture). Results show that the donut beam profile provides the most stabilizing effect as the energy sent to the material is balanced along a scanned line (thermal gradient minimized). The EBSD analysis of microstructures also reveals tiny modifications of grain structure and orientation with the use of modified beam shapes.
Speaker
Pierre Hébrard
Discover speaker profilePIMM Lab - Arts et Métiers, Paris, France
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36 - Comparative study of gaussian, top-hat and donut laser distribution for powder bed fusion additive manufacturing of AlSi10Mg alloy.
Date/Time
21/03/2024
12:05 pm -12:25 pm
Location
Room 6