ABSTRACT

Metal additive manufacturing processes, particularly laser-directed energy deposition (LDED), has been applied to synthesizing multi-component advanced materials for harsh environment usages for decades. High entropy alloys, generally consisting of 4 – 6 principal elements, have great potential to replace traditional alloys due to their synergistic high strength and ductility characteristics at cryogenic temperatures. LDED has been used for rapid and flexible synthesis of candidate high entropy alloys.

The purpose of this research is to establish a baseline understanding of the laser-directed energy deposition process and high entropy alloys as well as fabrication of high entropy alloys using LDED. The suitable principal elements for high entropy alloys to possess the desired characteristics ultimately depends on the physical and chemical properties of elements and microstructure of the fabricated high entropy alloys. Additional considerations of significance include the melting points of constituent metals and their independent lattice structures, status of feedstock powders, feed rate, and LDED parameters such as scanning speed, laser power, hatch spacing, and the absorptivity of constituent metals at the utilized laser frequency. Significant porosity and the buildup of residual stresses are notable defects of LDED that often require significant post treatment.