Outstanding yield strength of CoCrNiTa0.1 medium entropy alloy under the synergistic regulated with nanoprecipitation and grain refining

CoCrNi medium-entropy alloy (MEA) with equimolar multi-component has attracted much attention due to its promising comprehensive mechanical properties. However, the lack yield strength at room temperature limits its further engineering applications. In order to improve the yield strength at room temperature of CoCrNi MEA, tantalum (Ta) element with larger atomic radios and higher elastic modulus was added into CoCrNi MEA to produce precipitated strengthening phase, and CoCrNiTa0.1 MEA was designed and prepared. The CoCrNiTa0.1 MEA has outstanding yield strength of similar to 1339 MPa due to the fine grain strengthening and precipitation strengthening, which is much stronger than that of CoCrNi MEA. The as-produced alloy was composed of Ta-enriched Laves phase and fine-grained face-centered cubic (FCC) phase with certain amount of annealing twins. The small grains contributed to a superior fine grain strengthening up to about 434 MPa. The precipitated Ta-enriched Laves phase also greatly enhanced the alloy's mechanical strength. During the tensile deformation, nanoscale Laves phase particles interacted with the dislocations and annealing twins, hindering the deformation, and thus, significantly improved the yield strength. (C) 2022 Published by Elsevier B.V.

Automated summary

CoCrNiTa0.1 medium-entropy alloy shows outstanding yield strength of 1339 MPa, much higher than CoCrNi alloy, due to the combined effects of fine grain strengthening and precipitation strengthening. The alloy consists of Ta-enriched Laves phase and fine-grained face-centered cubic (FCC) phase, with small grains contributing to superior fine grain strengthening. The precipitated Ta-enriched Laves phase greatly enhances the alloy's mechanical strength.