Effect of Re and Ru on the phase stability and coarsening kinetics of L1(2) phase in a Ni29Co27Fe27Cr3Al7Ti7 high entropy alloy

The thermal stability of precipitates is a major concern for L1(2)-type strengthening high entropy alloy at elevated temperatures. In this study, we systematically investigated the effect of Re and Ru on the phase stability an d coarsening kinetics of L1(2) precipitates in the Ni29Co27Fe27Cr3Al7Ti7 HEA. The L1(2) phase exhibited a high volume fraction of 40.29% in the explored HEA and remained a stable morphology during the long-term exposure. Re addition did not change the volume fraction of L1(2) phase, while Ru addition decreased it to 34.42%. Both Re and Ru facilitated the formation of L2(1) precipitates slightly. Minor Re significantly decreased the coarsening rate of L1(2) phase and minor Ru also retarded the coarsening of L1(2) phase to some degree, which were mainly ascribed to the sluggish diffusion of Re and Ru atoms. These findings provide a feasible strategy to improve the coarsening resistance of L1(2) precipitates in HEA system through sluggish atomic diffusion. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that Re and Ru have certain effects on the stability and coarsening kinetics of the L1(2) phase in the Ni29Co27Fe27Cr3Al7Ti7 high entropy alloy. Both Re and Ru can promote the formation of L2(1) precipitates, and they reduce the coarsening rate of the L1(2) phase by slowing down atomic diffusion.