Mechanism guided identification for the next class of high-strength, temperature-resistant refractory multi-principal element alloys
Abstract
Developing the next generation of advanced turbine propulsion systems for far greater efficiency and powerdensity than todays superalloys highlights the long-standing challenge to design a material with highstrengthstability in high-temperature environments. With the advent of refractory multi-principal elementalloys (RMPEA), a promising solution had emerged. Since then, in search for suitable candidates, thedeformation mechanisms and yield strengths for a number of RMPEA compositions have been researchedand documented. Yet, to date, designing an ultra-strong RMPEA to resist high temperature degradationbased on simply thenumber, types, and ratios of elements constituting the RMPEA has not been performed.We initiate this project with the hypothesis that meeting this challenge lies in the fundamentalunderstanding of how dislocations move and the stress to move them at the scale of the glide plane. Thechallenges and opportunities in RMPEAs stem from both a)the flexibility in the choice of composition andprocessing parameters and b) the complexity in microstructures across multiple length scales. Especiallyunique to RMPEAs are the chemical and structural variations that fluctuate over the atomic and nanoscales.These length scales also span from those of the dislocation core to the length of the glide plane, suggestingthat such variations will profoundly affect basic dislocation processes. Numerous studies, utilizingnanomechanical testing, nanoscale characterization, or atomic-scale simulations, have provided evidenceof highly unusual, non-traditional dislocation motion (e.g., jerky glide, waviness) and pathways (e.g.,planar vs. wavy slip) in RMPEAs. However, the predictive capability that would link dislocation behaviorto slip strengths and ultimately to material str main goal is two-fold: a) build a data-driven computational tool capable of simulating minimumenergydislocation motion andpathways and calculating slip-plane constitutive responses in strainedRMPEAs and b) apply it to identify, in a high-throughput manner, RMPEA compositions for ultrahigh yieldstrengths stable over a broad range of temperatures, e.g., 1000 1600 C. We will target RMPEAs thatmeet the objective density and focus on composition variations in years 1 and 2 and the role of interstitialsand precipitates in years 3 and 4. Research activities will be driven to address four scientific questions:1. What are the unexpected dislocation behaviors in RMPEAs that lead to high temperaturestability?2. Is the effect of local chemical composition fluctuations in RMPEAs distinctive from thatof thermal fluctuations on dislocation motion?3. Can chemical compositions in RMPEAs affect the range of temperatures over which theeffects of local composition fluctuations dominate over thermal fluctuations?4. How does the response of a dislocation to interstitials and second phases change withtemperature and RMPEA composition?The technical approach builds on the phase field dislocation dynamics tool being developed by the PI. Theadvancements planned include introduction of thermallyactivated processes, experimentally informedshort-ranged order, and effects of interstitials and second phases, such as nanoprecipitates. This work willbe part of a larger team effort with Professors Clarke at the Colorado School of Mines and Hemker at JohnsHopkins University. As an educational institution, UCSB performs fundamental and unclassified research.Any data or information developed or provided by UCSB, including but not limited to publications andreports, shall be unclassified fundamental research exempt from dissemination controls or reviewrequirements.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 09, 2021
- Source ID
- N000142112536
Entities
People
- Irene J Beyerlein
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara