  High-entropy alloys (HEAs) are solid solutions of multiple elements with
equal atomic ratios which present an innovative pathway for de novo alloy
engineering. While there exist extensive studies to ascertain the important
structural aspects governing their mechanical behaviors, elucidating the
underlying deformation mechanisms still remains a challenge. Using atomistic
simulations, we probe the particle rearrangements in a yielding, model HEA
system to understand the structural origin of its plasticity. We find the
plastic deformation is initiated by irreversible topological fluctuations which
tend to spatially localize in regions termed as soft spots which consist of
particles actively participating in slow vibrational motions, an observation
strikingly reminiscent of nonlinear glassy rheology. Due to the varying local
elastic moduli resulting from the loss of compositional periodicity, these
plastic responses exhibit significant spatial heterogeneity and are found to be
inversely correlated with the distribution of local electronegativity. Further
mechanical loading promotes the cooperativity among these local plastic events
and triggers the formation of dislocation loops. As in strained crystalline
solids, different dislocation loops can further merge together and propagate as
the main carrier of large-scale plastic deformation. However, the energy
barriers located at the spatial regions with higher local electronegativity
severely hinders the motion of dislocations. By delineating the transient
mechanical response in terms of atomic configuration, our computational
findings shed new light on understanding the nature of plasticity of
single-phase HEA.
