Polycrystalline Multi-Principal-Element Alloys: Exploiting the Role of Grain Boundaries.
Abstract
In the last decade or so, the field of so-called high-entropy (HE) or multi-principal-element alloys (MPEAs) has seen exponential gr""owth, as it represents a paradigm shift in terms of how engineers and scientists think about alloy development. MPEAs typically comp"rise five or more elements such that the principal element is present at a concentration between 5 and 35%. These novelalloys have been found in some cases to exhibit unexpected crystal structures and superior mechanical properties. Despite some progress in this" area, basic understanding of many aspects of the physical properties of MPEAs is lacking. Although the grain boundary (GB) structur""e of a polycrystalline alloy is critical in defining properties such as microstructural stability, diffusional transport and deforma""tion behavior, prior work in this area is limited. The goal of this program is to elucidate the chemistry and structure of GBs in MP""EAs, and to identify the principles that dictate whether an element will segregate. Given the multi-component, entropy stabilized na""ture of the base compositions, this will be a complex question to address. Atomic segregation to dislocation cores, key to the inhib""ition of plastic deformation, will also be studied. Additionally, it is proposedto employ a novel strategy of incorporating composi"tionally-graded oxide particles designed to trap dislocations and enhance high temperature mechanical properties. Solid solution compositions from each of the main classes of MPEA alloys (3d transition metal and refractory metal) will be selected as the reference" base materials. The study will integrate advancedcharacterization techniques, novel processing, thermodynamic modelling, and simul"ation of dislocation dynamics. The outcomes will include the development of a fundamental framework for the design of MPEA compositions with improved microstructural stability and mechanical properties.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 26, 2018
- Source ID
- N000141812181
Entities
People
- Martin P Harmer
Organizations
- Lehigh University
- Office of Naval Research
- United States Navy