|About this Abstract
||2018 TMS Annual Meeting & Exhibition
||High Entropy Alloys VI
||Thermal Stability and Coarsening of Coherent Particles in a Precipitation-hardened (NiCoFeCr)94Ti2Al4 High-entropy Alloy
||Y.Y. Zhao, T.G. Nieh
|On-Site Speaker (Planned)
The coarsening and age hardening behaviors of a fcc-(NiCoFeCr)94Ti2Al4 alloy were studied at temperatures between 750 and 825 °C. The morphology of the γ’ coherent precipitates exhibits as Great Rhombicuboctahedron, which is consistent with the equilibrium shape of Ni3Al predicted by first-principles calculations. It was found that the coarsening of γ’ precipitates follows the classical Lifshitz–Slyozov–Wagner (LSW) theory for Ostwald ripening. The activation energy for the coarsening of γ’ precipitates was evaluated to be 278 kJ/mol, which compares favorably with the activation energy for diffusion of Al or Ti in Ni and Ni-based alloys, indicating diffusion of either Al or Ti or both controls the coarsening. The precipitation hardening behavior of the alloy was also analyzed, and the optimal precipitate diameter was determined to be ~ 25 nm.
||Planned: Supplemental Proceedings volume