Exploring additive manufacturing as a high-throughput screening tool for multiphase high entropy alloys

Abstract

High entropy alloys (HEA) exhibit exceptional and sometimes record-setting physical, thermal and mechanical properties. However, the vast composition space presents a significant practical challenge for optimization, particularly when relying on sequential use of conventional metallurgical fabrication and characterization methods. An efficient method for rapidly evaluating the properties of complex concentrated alloys is presented. Powder based directed energy deposition additive manufacturing was used to synthesize a broad range of compositions in a single metallurgical sample via in situ alloying. An investigation of the phase-property space was done by compositionally grading a transition metal-based HEA (CoCrFeMnNi) with several refractory metals (i.e., Ta, Nb, and Ti-6Al-4V). A high throughput microstructural-mechanical analysis method was also utilized to rapidly assess microstructure and hardness as a function of alloy composition. Compositions promoting solid solutions, multiple phases, and intermetallics were found to have a wide range of hardness and fabrication quality. These results are discussed in the context of alloy-specific microstructural characteristics and configurational entropy, along with relevant processing challenges.