Materials and manufacturing renaissance: Additive manufacturing of high-entropy alloys

The disruptive potential of additive manufacturing (AM) relies on its ability to make customized products with considerable weight savings through geometries that are difficult or impossible to produce by conventional methods. Despite its versatility, applications of AM have been restricted due to the formation of columnar grains, resulting in solidification defects and anisotropy in properties. To achieve fine equiaxed grains in AM, alloy design and solidification conditions have been optimized in various alloy systems. In this review paper, the microstructure of high-entropy alloy (HEA) parts produced by selective laser melting and powder-based directed energy deposition is investigated. Solidification maps based on laser process parameters (as opposed to most commonly used solidification velocity and temperature gradient) are constructed by compiling available literature for single-phase face-centered cubic, body-centered cubic, and multiphase HEAs. These maps could guide printing of HEAs and provide an insight into the design of novel HEAs for AM.