Phase stability and polymorphism in multi-principal-element alloys

Research Project, 2024 – 2027

Multi-principal-element alloys (MPEAs) with several metallic elements at (close to) equimolar concentration exhibit many unique properties, and are promising candiates for both structural and functional applications. Recently, in situ synchrotron diffraction experiments have revealed the existence of high-pressure phases in transition metal MPEAs with face centered cubic (fcc) crystal structure. This is surprising due to the complete absence of polymorphism in elemental fcc transition metals. Explanations in terms of pressure induced magentic moment supression have been proposed based on ab-initio calulations, but no conclusive experimental evidence exists today. In this project we will explore the origins of pressure-induced polymorphism in prototype MPEAs by in situ synchrotron-based characterization of element-specific magnetic moments. The goal is to directly correlate the suppression of magnetic moments with the onset of the transition. As the polymorphic transition depends on the relative thermodynamic stability of the phases, a clear understanding of the origin will directly shed light on the more general, and much debated, phase-selection criteria in this class of materials and allow targeted design of new materials with optmized structural and functional properties. As the project includes investigations of a larger compsotional space than have currently been investigated, the results will also serve as "expreimental ground truth" for future ab-initio calculations