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. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.