Equilibrium segregation in an antimony-containing stainless steel

Loss of grain boundary segregant during ion milling

It is shown that material segregated to grain boundaries can be lost during ion milling. This specimen preparation artifact has been studied in the case of bismuth in copper and has also been observed for phosphorus in stainless steel. The loss is associated with specimen heating during ion milling and can be alleviated by good clamping and cooling of the specimen during milling. Specimen heating permits grain boundary diffusion of the segregating element to the specimen surfaces with subsequent loss of segregant from the specimen by evaporation or sputtering during ion milling. Loss of bismuth during in situ heating to 200-300 degrees C is demonstrated. Therefore, care must be taken in specimen preparation for analytical electron microscopy measurement of such segregation. Similar effects may occur during ion milling of other materials, especially those where low thermal conductivity will result in high beam heating. In these cases, care must be taken to avoid loss of segregant during specimen preparation. Additional tests showed that no significant loss of segregant was observed during X-ray microanalysis, even at nominal room temperature and probe currents five-fold higher than that normally used for microanalysis.

Comparison of TEM and APFIM in microstructural characterization and interpretation: an overview

A comparison of transmission electron microscopy (TEM) and atom probe field-ion microscopy (APFIM) is presented with respect to the interpretation of complex microstructures, phase identification, determination of crystallographic order, and analysis of interfaces. The capabilities, spatial resolutions, and limitations of each technique are discussed with examples taken from combined analytical electron microscopy (AEM) and APFIM studies. Both techniques are extremely powerful for routine characterization of a wide range of materials, although care must be exercised in experimentation and interpretation. The combined use of TEM and APFIM is synergistic and extends their individual capabilities from the macro scale to the atomic level.