Identifying non-equiatomic high entropy bulk metallic glass formers through thermodynamic approach: A theoretical perspective

Identifying high entropy bulk metallic glasses (HEBMGs) through high entropy alloy philosophy has the potential to avert complications inherent to pinpointing bulk metallic glass forming compositions. Currently, the mixing enthalpy and topological strain parameter of a multicomponent alloy is a popular guideline to demarcate glass forming alloys from solid solution and intermetallic phase forming high entropy alloys. However, the discovered HEBMGs have relatively inferior glass forming ability (GFA) in comparison to the best glass former in a particular alloy system. The origin of such low glass forming ability can be traced back to their moderately higher liquidus temperature. Therefore there exists an opportunity to engineer non-equiatomic HEBMGs through modifying the composition of the constituent alloying elements. In this work, based on the thermodynamic modeling of two quinary alloy systems we demonstrate that the existence of large atomic size difference over broad compositional region is necessary condition for enhancing GFA in non-equiatomic HEBMGs. In addition, it is proposed that figuring out the prominent binary chemical interactions in the near equiatomic alloy composition is an effective approach to enhance GFA in these complex alloy systems.