Herein, CoCrFeNi high-entropy alloy thin films were successfully synthesized via solid-state alloying from Al6(CoCrFeNi)94 multilayer films, forming a CoCrFeNi-based solid solution phase with a face-centered cubic structure by optimizing Al content to prevent any oxide reaction. The microstructural and phase evolutions in the multilayer films were systematically investigated to understand the alloying behavior. Interestingly, it can be evaluated that the alloying elements could be diffused into layers, even those with nonconnected interfaces, through the grain boundaries owing to the presence of nanostructured columnar grains. Thus, these grain boundaries act as a network of diffusion paths for alloying elemental atoms to be homogenized throughout multilayer films and form the reactive phase regardless of the thermodynamic and kinetic prediction. Consequently, grain boundary diffusion–assisted solid-state alloying can be used to synthesize high-entropy alloy thin films for various multicomponent alloy systems by only controlling the layer thickness in multilayer films.
Bibliographical noteFunding Information:
This study was supported by the National Research Foundation (NRF) of Korea funded by the Ministry of Education (Grant Nos. NRF-2019R1A6A3A01092651 and NRF-2020R1A2C2101047 , 2020M3H4A3106736 , and 2021M3H4A6A01045764 ). E.S. Park was supported by an NRF of Korea grant funded by the Ministry of Science and ICT (NRF-2019M3D1A1079215 and NRF-2018M3A7B8060601). M. Kim was supported in part by the Louis Beecherl, Jr. Endowment Fund.
- Grain boundary diffusion
- High-entropy alloy film
- Multilayer thin film
- Solid-state alloying