A review study on thermal stability of high entropy alloys: Normal/ abnormal resistance of grain growth

Poor performance of advanced engineering materials, during long term servicing at high temperature, is closely related to thermal stability of the microstructures. Instability of the microstructures specially in respect of the grain size, deteriorates mechanical properties and also has a detrimental effect on physical and functional properties of the components. In this respect, any of the High Entropy Alloys (HEAs) as a promising candidate has attracted academic and industrial attention according to their excellent high -temperature resistance and thermal stability compared with conventional engineering alloys. In this study we investigated effect of alloying element, annealing conditions (temperature, time), and pre-treatment (cold working) on grain growth behavior of HEAs. The retarding/accelerating effect of sluggish diffusion, solute drag, local concentration fluctuation, Zener factor, stacking fault energy, second phases, and fine particles were discussed in details. Grain growth kinetics was investigated with emphasis on grain growth exponent (n) and correlated activation energy (Q). Effectiveness of Hall-Petch relationship was finally studied to consider the frictional stress and slip transition behavior across grain boundaries. This review, overall, indicates high thermal stability of HEAs and also which one's high capability to be considered in high temperature engineering applications. & COPY; 2023 Elsevier B.V. All rights reserved.