Figure 5. Deformation and fracture in a semibrittle Au NWs with bimodal twin structures.

(a) Pristine Au NW with a bimodal twin structure as marked out by dash lines in yellow from TB₁ to TB₇. (b) As deformation proceeds, dislocations are observed to homogeneously nucleate in the segment with the largest twin thickness. The dislocations propagate and are blocked by the neighbouring TBs, causing strain-hardening. (c) Shear localization-induced necking formation under tensile loading, as marked out by the red arrows. Inset: Close-up on a partial dislocation with SF propagating along the radial direction from the neck, which softens this region and accelerates failure. (d) Fracture morphology of semibrittle fracture with de-twinned tips. Main scale bar, 5 nm; Inset scale bar in c, 1 nm.