Role of Particle Size Distribution on Microstructure, Defects, and Mechanical Properties in Laser-Based Powder Bed Fusion of Scalmalloy®

Abstract

This study investigates the impact of particle size distribution (PSD) in Scalmalloy® powder feedstocks on the geometrical accuracy, microstructure, defect formation, and mechanical properties of test artifacts fabricated via laser-based powder bed fusion of metals (PBF-LB/M). Two powder feedstocks were analyzed: Powder-1, with a mean particle size of 29.30–29.72 µm and a narrower, more uniform PSD, and Powder-2, with a mean particle size of 40.80–41.53 µm and a broader, more heterogeneous PSD. Powder-2 produced artifacts with improved geometrical accuracy and surface finish but exhibited cracking in both lattice (small features) and bulk regions. Scanning electron microscopy revealed Si precipitation near cracks in the lattice regions, attributed to segregation caused by heat accumulation in thin features and the coarser, more heterogeneous PSD of Powder-2. Powder-2 samples exhibited higher strain at a break during tensile testing, likely due to its lower porosity compared to Powder-1. Single-line and hatch scan results indicated no cracking for either powder, highlighting the susceptibility of small features to thermal gradients, segregation, and geometric stress concentrators. The observation of cracking exclusively in the thin features, and not in the bulk regions, underscores the artifact's utility in investigating how geometrical features influence thermal fields, microstructural evolution, and ultimately, performance in PBF-LB/M processes.