Delivering microstructural complexity to additively manufactured metals through controlled mesoscale chemical heterogeneity

Laser powder bed fusion (LPBF) of metals is a popular mode of additive manufacturing (AM) that has the advantage of producing complex shapes with little or no additional processing. However, a limitation is that the microstructures obtained are relatively simple solidification structures and there are few means available to enrich this. This limits the microstructural complexity that can be achieved and hence the properties obtainable. In this work, we present and validate a physically-based model to predict the chemical distribution resulting from LPBF of physically mixed powders of different compositions. We demonstrate that mixing of powders with different compositions can be used to generate a deliberately controlled, mesoscale chemical heterogeneity in LPBF that allows the formation of multiphase microstructures and delivers new microstructural complexity to LPBF. A duplex stainless steel, consisting of equal fractions of ferrite and austenite in the as-built state is used as a demonstration of the approach. This opens up a new path for delivering microstructural complexity to LPBF of metals.