First-principles study on mechanical properties in high entropy alloys

Tsuru, Tomohito   ; Lobzenko, I.   ; Shiihara, Yoshinori*; Wei, D.*; Yamashita, Shinichiro   ; Itakura, Mitsuhiro  ; 10 of others*

High entropy alloys (HEAs) are chemically complex single- or multi-phase alloys with crystal structures. There are no major components but five or more elements are included with near equiatomic fraction. In such a situation, deformation behavior can no longer be described by conventional solid solution strengthening model. Some HEAs, indeed, show higher strengthening behavior and anomalous slip. However, the mechanisms of these features have yet to be understood. Dislocation structure and motion should be the key to identify the unique feature of mechanical properties of HEAs. In the present study, we investigated the core structure of dislocations in body centered cubic (BCC) HEAs using density functional theory (DFT) calculations. The Random structure and ZrNbTaTiHf and the SRO structure obtained from the 800 K MC calculation in two BCC-HEA MoNbTaVW was prepared. Then, the energy distribution when the dislocation dipoles were introduced at 135 sites were calculated. We found that the dislocation formation energy is smaller in ZrNbTaTiHf, which has a large difference in MSAD and a large lattice distortion.