The x-ray mapping results with WDS techniques were confirmed by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). Figure 10 contains TOFSIMS images and confirms that silver and copper are non-uniformly distributed around dendrite arms. The analyst reported that gold and silicon displayed uniform distributions but the silicon levels were too low for valid conclusions to be reached. As in x-ray mapping, light areas are regions of high concentration and dark areas are regions of low concentration of the elements that are being observed.
Quantitative analyses at various locations within the dendritic structures were performed by electron microprobe techniques at two different laboratories. The metallographic sample used for backscatter imaging in Figure 8 was also used for this exercise. The nominal composition of the alloy is given in Table 1. The horizontal line in the photomicrograph in Figure 8 indicates the path that the microprobe beam followed across the sample.