Characteristic features of slip bands in submicron single-crystal gold component produced by fatigue

In order to investigate the fatigue behavior of submicron metal components, a resonant fatigue experiment is conducted using a single-crystal gold specimen that possesses a test section with a submicron width. Crystallographic slip bands appear on the test section surface due to fatigue when the resonant frequency of the specimen decreases abruptly. These slip bands form due to activation of a slip system with the maximum resolved shear stress amplitude. The critical value for slip band formation is evaluated to be over 150 MPa, which is over six times larger than that of persistent slip bands (PSBs) in the bulk counterpart. Cross-sectional field-emission scanning electron microscopy observations reveal that extrusions/intrusions that are ～15 nm wide form on the surface at slip bands. Although the slip bands have similar morphologies to those of PSBs, they are much narrower (bulk width is larger than 1 μm). The high fatigue strength may be attributed to the narrow slips required. Strain localization at the slip bands is revealed by cyclic deformation in the surface-polished specimen after fatigue. This suggests that there may be a certain fatigue understructure at the slip bands.