  Amorphous grain boundary complexions act as toughening features within a
microstructure because they can absorb dislocations more efficiently than
traditional grain boundaries. This toughening effect should be a strong
function of the local internal structure of the complexion, which has recently
been shown to be determined by grain boundary crystallography. To test this
hypothesis, molecular dynamics are used here to simulate dislocation absorption
and damage nucleation for complexions with different distributions of
structural short-range order. The complexion with a more disordered structure
away from the dislocation absorption site is actually found to better resist
crack nucleation, as damage tolerance requires delocalized deformation and the
operation of shear-transformation zones through the complexion thickness. The
more damage tolerant complexion accommodates plastic strain efficiently within
the entire complexion, providing the key mechanistic insight that local
patterning and asymmetry of structural short-range order controls the
toughening effect of amorphous complexions.
