Effects of Recycled Powder on Solidification Defects, Microstructure, and Corrosion Properties of DMLS Fabricated AlSi10Mg

This study examines the impacts of using recycled powder on solidification defects, microstructures, and the resultant corrosion properties of direct metal laser sintered AlSi10Mg alloy. Microstructural analysis confirmed that using recycled powder in the fabrication of AlSi10Mg leads to (1) an increased volume fraction of internal porosities and solidification micro-cracks, and (2) more coarsening of the interdendritic eutectic-Si network particularly along the melt pool boundaries, which were correlated to the larger size and irregular shape of the recycled powders compared to the virgin powders, leading to the reduced thermal conductivity of the recycled powders. To investigate the impacts of the above-mentioned microstructural changes on the corrosion performance of the alloy, anodic polarization testing and electrochemical impedance spectroscopy in aerated 3.5 wt.% NaCl solution were performed. The results confirmed a slight degradation of the corrosion properties of the recycled-powder fabricated samples, ascribed to further coarsening of Si-network along their melt pool boundaries.