The early stages of plastic yielding in polycrystalline gold thin films

We present transmission electron microscope observations of the effects of stress in polycrystalline gold thin films. The films exhibit a very strong {111} fiber texture, and are loaded in biaxial tensile stress. Under these conditions, each grain exhibits the same Schmid factor, within a very small variance. Despite the identical loading conditions and resolved shear stresses from grain to grain, we observe that yield is isolated in only a few grains. Yield initiates only at specific triple junctions, and we identify the conditions required for a triple junction to be active in this manner. The required conditions for yield to occur at a triple junction include (1) an appropriate slip-plane inclination relative to the grain boundaries at the junction; and (2) at least one grain boundary of appropriate character, adjacent to the slip plane specified in item 1.