Influence of atomic radius ratio of constituent elements on high entropy alloying

High-Entropy Alloys (HEAs) are defined as solid solutions with high mixing entropy due to mixing generally more than five constituent elements in an equiatomic or near-equiatomic fraction, show both high strength and high ductility. The high strength is possibly realized by lattice distortion caused by mixing atoms with different their radius; hence, the strength increases with the atomic radius ratio δ. However, from some experiments, it has been also reported that single-phase solid solutions of HEAs transform into multiphase to amorphous with increasing of δ. These results show that the increase of δ is likely not only to make HEAs stronger, but also to change HEAs amorphous alloys. The purpose of this research is to establish the atomic modeling of HEAs, which is necessary to investigate the strengthening mechanism of HEAs via atomic simulations. We use five constituent-elements systems with different atomic radii to express various values of δ. As the result, we revealed that the proportion of crystal regions maintains near 1 until δ reaches 6, but amorphous regions increases with δ over 6. Furthermore, although the degree of mixing of the first neighbors in crystal regions is constant when δ < 10, the degree of mixing in amorphous regions tends to decrease monotonically regardless of δ. This result implies that the defects in HEAs consist of specific atomic groups.