Thermomechanical processing of refractory multi-principal element alloys for ultrahigh temperature performance
Abstract
Refractory multi-principal element alloys (RMPEAs) hold exceptional promise for ultrahigh temperature performance, beyond conventional Ni- and Co-based and refractory alloys, needed for advanced turbine engines and hypersonic flight. A major barrier to the implementation of any refractory alloy, beyond its high temperature performance, is its ability to be manufactured by conventional practices like wrought (thermomechanical) processing, given the limited workability of refractory alloys at lower temperatures. Here we propose to fundamentally understand microstructure evolution and deformation mechanisms in selected RMPEAs with promising ultrahigh temperature performance during thermomechanical processing over 1000 C, including the effects of oxygen and carbon. This is at its infancy for RMPEAs, but is necessary for the development and deployment of RMPEAs for DoD applications. We hypothesize that thermomechanical processing can be used to control RMPEA microstructural development and characteristics important to ultrahigh temperature performance. In this work, we seek to address the following questions: 1.0 What microstructures are produced during thermomechanical processing, including the extent of recrystallization, at elevated temperatures over 1000 C in compression and tension at different strain rates? And, can high-temperature deformation mechanism and processing maps be made for selected RMPEAs?; 2.0 What effects do interstitial oxygen and carbon have on microstructure development during thermomechanical processing, and do precipitates form? Sub-questions include: Do interstitials interact with defects (i.e., dislocations) and/or impact recrystallization behavior? Does increased oxygen result in the formation ofdeleterious, benign, or beneficial oxides? Can increased carbon be strategically used to produce beneficial carbides in novel RMPEAs (i.e., a designed multiphase microstructure) that provide precipitation strengtheved creep behavior at high temperatures? Might carbides also advantageously control grain size (e.g., precipitation is used in modern microalloyed steel products) during thermomechanical processing?; 3.0 What are the key microstructural characteristics (grain sizes and distributions, crystallographic texture, dislocation substructure, precipitation, etc.) produced by thermomechanical processing and heat-treatment, and can they be controlled?Thermodynamic, kinetic, and solid solution strengthening modeling will be performed at the Colorado School of Mines tofacilitate RMPEA selection (the elements Nb, Ta, W, Mo, V, Hf, Zr, Ti, and Cr will be considered, without/with intentionally increased oxygen and carbon), in addition to alloy fabrication, thermomechanical processing in compression and tension at temperatures over 1000 C with strain rate variations, heat treatments and controlled heating/cooling in the dilatometer, and multiscale in-situ/ex-situ characterization (e.g., electron microscopy, differential scanning calorimetry, x-ray diffraction) to fundamentally understand microstructure evolution and deformation mechanisms relevant to ultrahigh temperature performance. This work will generate data for database development to help build an Integrated Computational Materials Engineering (ICME) infrastructure and integrate with modeling and experiments being performed at the University of California Santa Barbara and Johns Hopkins University. The proposed foundational work will be essential for the accelerated development and deployment of RMPEAs for turbine propulsion systems, and will provide important insights relevant to RMPEA thermomechanical processing and manufacturing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 09, 2021
- Source ID
- N000142112535
Entities
People
- Amy Clarke
Organizations
- Colorado School of Mines
- Office of Naval Research
- United States Navy