Temperature gradient enhances the solidification process and properties of a CoCrFeNi high-entropy alloy: Atomic insights from molecular dynamics simulations

Material properties are substantially affected by the process during fabrication. To what extent for high-entropy alloys (HEAs), however, is still an open question. Herein, we investigated the effect of a temperature gradient on the solidification of a CoCrFeNi HEA using molecular dynamic simulations. The nucleation and crystal growth under gradient temperatures significantly differ from those under homogeneous temperatures. The HEA solidified by a temperature gradient forms a single and uniform face-centered cubic (FCC) crystalline phase, and the residual stresses in the solidified tissue are optimized. During the homogeneous solidification process, in addition to the FCC phase, the hexagonal close-packed (HCP) phase and a small amount of body-centered cubic (BCC) phase were also formed. When the temperature gradient is 100 K, the stress distribution in the solidification microstructure is relatively low. Increasing the temperature gradient can enhance the crystallinity of the solidification microstructure. While, an increase in cooling rate will lead to a reduction in the crystallinity of the solidification microstructure and an increase in internal stresses within the solidification microstructure. A slight short-range order (SRO) phenomenon present in both solidified structures. Our atomistic insights might be helpful in the fundamental understanding and material design of HEAs.