High-Entropy Alloys: Formation and Properties

Abstract

This paper presents ongoing research at NETL aimed at gaining fundamental understanding of high-entropy alloys (HEAs) formation and their properties, and developing highperformance HEAs for high-temperature fossil energy applications. First-principles density functional theory (DFT), Monte Carlo simulation, and molecular dynamics simulation are carried out to predict enthalpy of formation, the entropy sources (i.e., configurational entropy, vibrational entropy, and electronic entropy), and elastic properties of model single-phase HEAs with the face-centered cubic, body-centered cubic and hexagonal closed-packed structures. Classical elastic theory, which considers the interactions between dislocations and elastic fields of solutes, has also been used to predict solid solution strengthening. Large-size (∼7.5 kg) HEAs ingots are produced using vacuum induction melting and electroslag remelting methods, followed by homogenization treatment resulting in greater than 99% homogeneity. Subsequent thermomechanical processing produces fully-wrought face-centered cubic microstructures. The tensile behavior for these alloys have been determined as a function of temperature, and based on these results screening creep tests have been performed at selected temperatures and stresses.