โ Scribed by J Bruley; V.J Keast; D.B Williams
No coin nor oath required. For personal study only.
AbstractรGrain-boundary segregation is a necessary, but not always sucient, criterion for intergranular embrittlement of many metals and alloys. The reason why certain segregants induce embrittlement while others are harmless remains unclear, but it has been theorized that segregation may be responsible for local changes in the atomic bonding which, in turn, may produce brittle failure. Recent developments in electron energy-loss spectrometry in the analytical electron microscope permit correlation to be made between the presence of certain segregants and changes in the bonding of the atoms on the grain boundary. Because the eects in the energy-loss spectrum are small, the spatial-dierence method (equivalent to a ยฎrst-dierence spectrum) is sometimes used to discern the spectral intensity changes. It is important to ensure that this method of processing the data does not induce the changes in the spectrum that are usually associated with changes in bonding, and this can be demonstrated by experimental comparison of energydierence and spatial-dierence spectra. Using direct measurement, as well as spatial-dierence techniques, it is demonstrated that Bi and Sb, well-known embrittlers of Cu, induce consistent changes in the bonding of Cu, while Ag, a similar segregant which does not embrittle Cu, produces no detectable changes in the bonding.
๐ SIMILAR VOLUMES
The distribution of segregation levels of bismuth to grain boundaries in copper has been measured and compared using Auger electron spectroscopy (AES) and X-ray energy-dispersive spectroscopy (XEDS) in a scanning transmission electron microscope (STEM). The STEM-XEDS measurements showed that there a