Comprehensive understanding of local lattice distortion in dilute and equiatomic FCC alloys

Abstract

Quantifying the local lattice distortion (LLD) and exploring its correlation with material properties are of fundamental importance for the design of high entropy alloys (HEAs). In the present work, we expressed the LLD as the standard deviation of the bond lengths (SDBL). With which, we calculated the LLDs of the face-centered cubic (fcc) alloys, including the dilute and equiatomic binary TM-Co and TM-Ni (TM = transition metal) alloys and the equiatomic CrMnCoNiFe family HEAs by using a first-principles method. For the binary TM-Co and TM-Ni alloys with TM in the same period of the Chemical Element Periodic Table, the LLD and the number of valence electrons of TM exhibit roughly a parabolic relationship with a minimum in the middle of the period. For the HEAs involved in the present work, the composition-LLD-mechanical property relationship was constructed. It is found that the experimental yield strengths increase monotonically with the calculated LLDs, and to pursue a high LLD in the CoNi-based CrMnCoNiFe family alloys, one should increase Cr to an appropriate content and avoid introducing Fe. Furthermore, the influences of the atomic radius, electronegativity, and magnetism on the LLD were elucidated. The present work provides a comprehensive understanding of the LLD in both dilute and equiatomic FCC alloys.