Selected Observations of Phase Equilibria and Diffusion Kinetics in Metallic Alloys Additively Manufactured by Laser Powder Bed Fusion

Additive manufacturing of metallic alloys, for example, laser powder bed fusion (LPBF), is a transformative technology that can produce engineering components with nearly unlimited geometrical complexity and functional customization. Emergence of technology also brings an opportunity to develop new and modified alloys specifically for thermo-kinetic environment associated with LPBF, requiring fundamental understanding of phase stability, diffusion kinetics and solidification. Selected observations of microstructural development such as grain structure, composition-sensitive solidification cracking, sub-grain micro-segregation, homogenization, and precipitation will be highlighted for additively manufactured Al-, Mg-, Ni-, and Fe-base alloys, produced from gas atomized alloy powders made for both commercial and experimental use. Practical use of phase diagrams and diffusion kinetics in designing and modifying the alloy composition for the enhanced buildability and properties will be presented with experimental corroboration.