Composition-dependent grain growth kinetics of Ni-Co-Cr-Fe high-entropy alloys

Grain size refinement is one of the most effective and feasible approaches to tailor the mechanical properties of metals and alloys. This classic strengthening mechanism is recently highlighted in Ni-Co-Cr-Fe-based high-entropy alloys due to its extremely large Hall-Petch coefficient of 1100 MPa<middle dot>mu m(1/2). However, the grain growth kinetics of Ni-Co-Cr-Fe, which serve as the guideline for controlling the grain size of related high-entropy alloys (HEAs), are still unclear. Here, we investigated the grain growth behaviors of Ni2CoCrFe, NiCo2CrFe, and NiCoCrFe2. Our results show that the grain growth kinetics of Ni-Co-Cr-Fe are highly dependent on the concentration of its principal elements. The grain growth activation energies are 315, 622, and 570 KJ/mol for Ni2CoCrFe, NiCo2CrFe, and NiCoCrFe2, respectively. This big difference is mainly attributed to the degree of grain boundary segregation caused by the interactions between different atomic pairs. These findings are helpful for designing HEAs with controllable microstructures.