Influence of powder size on defect generation in laser powder bed fusion of AlSi10Mg alloy

The particle size distribution (PSD) often changes as powders are cycled for recycled and different powder batches are used, challenging a critical aspect of quality assurance in the Laser Powder Bed Fusion (LPBF) process. It is therefore important to understand how powder PSD affects the processability of powder in the context of LPBF. In this work, a batch of AlSi10Mg powder was sieved into four sets of powder with controlled PSD (D50 ranging from 16 μm to 76 μm). Single-track and cuboid samples were made from powders with variations in laser power whiling fixing other laser processing parameters constantly. It is shown that coarser powders are much more sensitive to changes in laser power in terms of melt pool characteristics, defect population and size, showing significant improvements in relative density upon increasing laser power. The simulations reveal with the combination of low laser power and coarse powders, pores mainly originate from insufficient melting of powders at the sides of melt pools due to insufficient and inhomogeneous absorption of laser energy. It is possible to achieve nearly fully-dense parts when processing coarse powders given that the incident laser beam energy is sufficient.