EFFECT OF TRACE-ELEMENT ADDITIONS ON THE GRAIN-BOUNDARY COMPOSITION OF IR + 0.3 PCT-W

The grain boundary fracture surfaces of several Ir + 0.3 pct W alloys have been examined using Auger electron spectroscopy. Dopant additions (between 10 and 80 wt ppm) of Al, Fe, Th, Ni and Rh are shown to result in thorium enriched grain boundaries. Inert ion sputtering experiments suggest that the thorium enriched region at the grain boundaries is probably only a few atom layers thick. The other dopants (Al, Fe, Ni and Rh) do not appear to influence the segregation of thorium, and their function (if any) in improving the high temperature impact properties of this alloy is unclear at this time. © 1979 American Society for Metals and The Metallurgical Society of AIME.