Synthesis and Processing of Materials, Stabilizing Nanoalloys at High Temperatures via Utilizing High_Entropy Grain Boundaries.
Abstract
Nanocrystalline materials have generated great research interests due to their potentials to achieve superior properties. However, such materials are generally prone to grain growth at low or even room temperatures, rendering them impractical for many applications. Inhibiting grain growth becomes a greater challenge at higher temperatures. Built on the success of recent original work in the PI group, the proposed project aims to exploit a potentially-transformative concept of utilizing high-entropy grain boundaries (HEGBs) to stabilize nanocrystalline alloys (nanoalloys) at high temperatures (above 1000 C). The central scientific hypothesis is that HEGBs can be utilized to greatly increase the temperature stability of nanoalloys, thereby enabling their applications at high temperatures. More specifically, HEGBs can accommodate more adsorption within the bulk solid solubility limit, which can (i) not only reduce grain boundary energy as the thermodynamic driving force for grain growth (ii) but also enlarge the solute-drag effect to inhibit grain growth. Such HEGB-enhanced adsorption can be utilized to counter the detrimental temperature-induced desorption, thereby stabilizing nanoalloys at high temperatures. In addition to Type I multinary nanoalloys (with one principal and multiple segregating elements), bulk high-entropy effects in Type II high-T stable multinary nanoalloys (with multiple principal and one or more segregating elements) can lower the bulk chemical potentials to suppress precipitation to enable more grain boundary adsorption within the bulk solid solubility limit. The newly-proposed stabilization mechanisms in both Type I and Type II multinary nanoalloys have the same physical origin: to promote grain boundary adsorption with respect to the precipitation of secondary phases, thereby decreasing the grain boundary energy and increasing the solute drag. This project aims to validate the above scientific hypothesis and further establish a new coupled thermodynamic and kinetic theory and associated models to guide the design of new HEGB-stabilized high-T nanoalloys. In an additional high-risk and high-return thrust, amorphous-like HEGBs will be exploited to stabilize multinary nanoalloys to even higher temperatures. Using Ni-based multinary nanoalloys as the initial model system, this project will (1) develop a new coupled thermodynamic and kinetic theory and associated models for HEGBs, conduct both (2a) numerical and (2b) physical experiments and characterization to validate the hypothesis and models, and further (3) develop criteria for selecting alloying elements to stabilize nanoalloys at high temperatures via utilizing HEGBs. The model system(s) for experiments may be adjusted based on the initial experimental feedbacks. The successful completion of this project will establish a new theoretical framework that is transferable to a broad range of other materials to enable the use of HEGBs to stabilize nanoalloys at high temperatures, with broad technological impacts.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 24, 2023
- Source ID
- W911NF2210071
Entities
People
- Jian Luo
Organizations
- Army Contracting Command
- United States Army
- University of California, San Diego