Cyclic deformation behaviors of fcc metals, especially Cu and Ag single crystals were compared. It is found that the dislocation patterns of fatigued Cu and Ag single crystals display similar feature with ladder-like persistent slip bands (PSBs). The current finding confirms that, after Cu and Ni, Ag is the third pure fcc metal to form the ladder-like PSB structure. Different geometric scales corresponds to the two-phase models with different physical meanings, Based on the two-phase model of the microscopic scale, a new criterion for PSB formation has been established. (SEE Li P et al., Acta Mater., and Li P et al., Scripta Mater., 59 (2008) 730-733)

Figure: Schematic diagram of the typical saturation dislocation patterns in cyclically deformed fcc crystals on (a) a macroscopic, (b) a mesoscopic and (c) a microscopic scale.