Critical review of the state of the art in multi-material fabrication via directed energy deposition

Directed energy deposition (DED) is an additive manufacturing technique that employs laser melting to permit for the free form manufacturing of components from many input materials from powder or wire form of feedstock. The nature of DED processes and advancements thereof has led to research that has been aimed at leveraging this additive manufacturing technology for the fabrication of high-value metallic alloys in addition to the exploration of multi-material composites and components - many of which are only possible to produce via DED. Herein, a critical review of the present body of research regarding DED of multi-materials is presented. Assessed are the developing research trends, design methodologies, common issues and challenges, as well as identification of the areas where further research should be directed.