Interactions between screw dislocation and twin boundary in high-entropy alloy: A molecular dynamic study

The interaction between dislocations and twin boundaries plays an important role in the plastic deformation of high-entropy alloys (HEAs), in which deformation twinning mechanisms are highly active. However, research concerning the twinning-induced strengthening in HEAs is lacking, especially atomistic studies. Therefore, molecular dynamics (MD) simulations are performed to elucidate the interaction mechanisms between the screw dislocation and the coherent twin boundary in the CoNiCrFeMn HEA and pure Ni. Dislocation transmission across the twin boundary is observed as the only mode in the CoNiCrFeMn HEA and pure Ni. However, the Shockley partial dislocations cannot simultaneously constrict on the twin boundary in the CoNiCrFeMn HEA because of the nanoscale segment detrapping mechanism related to the statistical fluctuation of chemical ordering, different from that in pure Ni. To quantify the interaction mechanism, generalized stacking fault energies and lattice friction are considered for predicting the interaction mode in the CoNiCrFeMn HEA. A new material parameter that considers the negative stacking fault energy and large lattice friction stress is proposed for the CoNiCrFeMn HEA.