“High-entropy alloys: Fundamentals of mechanical behavior”
High-entropy alloys (HEAs) are a relatively new class of materials that are mixtures of four, five, or more elements in near-equal amounts. They stand in stark contrast to conventional alloys that consist of a primary element chosen with a primary property in mind to which secondary elements are added for other properties. HEAs are scientifically interesting because textbook theories developed for dilute solid solutions break down in equiatomic alloys lacking “solvents” or “solutes.” Additionally, some HEAs also have outstanding mechanical properties including the highest fracture toughness of any material class, combined with good strength and ductility, all of which increase as the temperature is decreased. In this talk I will elucidate the fundamental factors and mechanisms that govern the mechanical behavior of these complex alloys by focusing on a few carefully processed model systems. Wherever possible, compositional effects on strength and ductility will be rationalized in terms of their effects on basic physical properties such as elastic constants and stacking fault energies. I will also touch upon some fruitful directions for future research.