Influence of particle size distribution and morphology on the properties of the powder feedstock as well as of AlSi10Mg parts produced by laser powder bed fusion (LPBF)

Abstract

The present paper aims to generate a deeper understanding of the influence of powder properties on the final parts manufactured by metal LPBF processes at constant parameter settings, except the hatch scanning speed. This issue was considered using four different AlSi10Mg powders.In addition to particle properties, such as particle size distribution and morphology, typical properties of the powder feedstock like bulk and tapped density, Hausner-Ratio, flowability and laser absorption were measured. Furthermore, the in situ density of the powder layers applied during the LPBF process were analyzed. A comparison of the surface quality, part density and mechanical properties of AlSi10Mg parts produced by LPBF, using different particle size distributions and morphologies, has been conducted. Within the processing experiments, the laser scanning speed was varied in order to achieve the most economical manufacturing of parts with a density > 99.2 %.Following this comparison, it was found that the manufacturing process of the powder and therefore the particle morphology has the biggest impact on the part density and surface quality. The considered plasma atomized powder could be processed at a higher scanning speed without a significant decrease in mechanical properties or part density. Generally, it was shown that higher densities of the powder layer result in higher part densities. However, the layer densities for powders which show almost the same bulk density can differ significantly and do not reach the regarding bulk density value. Therefore it can be stated that the layer density is not only affected by the bulk density. In terms of surface quality, the investigated plasma atomized powder provides a significantly lower surface roughness.Moreover, it was found that the measurement of the laser absorption shows a strong correlation to the achievable part densities. In contrast to the other methods performed, it was the only measurement that is very sensitive even to small variations of the powder and enables an unequivocal differentiation of the examined powders.