Abstract: The short-range ordering (SRO) structure has been considered as a toughening method to improve the mechanical properties of high-entropy alloys (HEAs). However, the strengthening mechanism of the SRO structures on the HEAs still needs to be further revealed. Here, the effect of element distribution, Al content, crack orientation, temperature, and strain rate on the crack propagation behavior of the Al_xFeCoCrNi HEAs are investigated using Monte Carlo (MC)/molecular dynamics (MD) simulation methods. Two HEA models are considered, one with five elements randomly distributed in the alloys, i.e. RSS_HEAs, and the other presenting SRO structure in the alloys, namely SRO_HEAs. The results show that Al atoms play a decisive role in the SRO degree of the HEA. The higher the Al content, the greater the SRO degree of the HEA, and the stronger the resistance of the SRO structure to crack propagation in the alloys. The results indicate that the reinforcement effect of the SRO structure in the model with the ($1\bar{1}\bar{1}$)[110] crack is more significant than that with the ($\bar{1}10$)[110] crack. The results show that the crack length of the alloys at maximum strain does not monotonically increase with temperature, but rather exhibits a turning point at the temperature of 400 K. When the temperature is below 400 K, the crack length of the alloys increases with the increase of temperature, while above 400 K, the opposite trend appears. In addition, the results indicate that the crack length of the alloys decreases with increasing strain rate under the same strain.

Key words: Short-range order, High-entropy alloys, Crack propagation, Crack orientation, Molecular dynamics simulation