Cyclic deformation and fatigue damage behaviors of oriented Ag single crystal

Abstract

The cyclic deformation and fatigue damage behaviors of oriented Ag single crystal were investigated in terms of cyclic stress–strain (CSS) curves, surface slip morphologies and dislocation configurations. A clear plateau region appears in the CSS curve of the Ag single crystal over a strain range of with average saturation shear stress amplitude of ∼26.6 MPa. Corresponding ladder-like persistent slip bands (PSBs) also appear in the Ag single crystal. Compared with other Cu and Ag single crystals with single or double-slip orientations, the saturation resolved shear stresses of the critical double-slip-oriented single crystals, no matter whether for Cu or Ag, are significantly higher than that of the single-slip-oriented ones. Combining the two-phase model with the hindering effect of sessile jogs on screw dislocation movement, a three-phase model is proposed to rationalize the increase of saturation stress. In addition, the surface slip morphologies of the Ag single crystal were characterized by the interactions between the primary and secondary SBs. According to the difference in their slippage, their interactions can be divided into three types, which could simultaneously appear in different local areas of the same crystal. The current experimental results extend the fundamental understanding of the intrinsic fatigue damage behaviors of fcc metal crystals.