Combined effects of solute drag and Zener pinning on grain growth of a NiCoCr medium-entropy alloy

Coarse grains are formed during thermomechanical processing for the widely studied NiCoCr medium-entropy alloy (MEA) due to the lack of effective approaches to restrain grain growth. Here, a novel integrated method combing solute drag and Zenner pinning effects are proposed. The 0.5 at.% C was added to precipitate carbides which generates pinning of the grain boundaries; while solute drag is implemented by 3 at.% addition of Mo with low self-diffusion coefficient. Results show that most of Mo is dissolved in the matrix and M23C6 carbides uniformly precipitated after aging. The combined method shows a significant effect on controlling grain growth and results in much finer equiaxed grains. A very high growth activation energy of 511 kJ /mol was obtained, double that of NiCoCr MEA (251 kJ/mol). This work shows that the grain growth kinetics of the NiCoCr based MEA during traditional thermomechanical processing can be tuned by adjusting carbide precipitates and selecting appropriate solute elements.

Automated summary

A novel integrated method combining solute drag and Zenner pinning effects is proposed to control grain growth in NiCoCr medium-entropy alloy, resulting in much finer equiaxed grains. The high growth activation energy obtained shows the effectiveness of this method in tuning the grain growth kinetics during traditional thermomechanical processing.