Fine second-phase particles, numerous in sintered alpha-SiC, were analyzed by scanning Auger microscopy and conventional techniques. The Auger analysis utilized computer-controlled data acquisition, multielement correlation diagrams, and a high spatial resolution of 100 nm. This procedure enabled construction of false color maps and the detection of fine compositional details within these particles. Carbon, silicon oxide, and boron-rich particles (qualitatively as BN or B4C) predominated. The BN particles, sometimes having a carbon core, are believed to result from reaction between B4C additives and nitrogen sintering atmospheres.

While scanning Auger micrographs are used extensively for illustrating the stoichiometry of complex surfaces and for indicating areas of interest for fine point Auger spectroscopy, there are many problems in the quantification and analysis of Auger images. These problems include multiple contrast mechanisms and the lack of meaningful relationships with other Auger data. Collection of multielemental Auger images allows some new approaches to image analysis and presentation. Information about the distribution and quantity of elemental combinations at a surface are retrievable, and particular combinations of elements can be imaged, such as alloy phases. Results from the precipitate hardened alloy A1-2124 illustrate multispectral Auger imaging.

Additional hot stage Auger experiments have provided surface segregation data for NiCrAl + or - Y or Zr alloys in agreement with other investigations. This data, combined with experimental and theoretical evidence of the Al2O3-metal bond strength, is presented in support of a chemical mechanism of Al2O3 scale adhesion. Both the detrimental effects of sulfur segregation and the beneficial effects of dopant segregation may be important. Chemical features of the dopants are compared in light of these proposed mechanisms, namely delta H sub f (sulfide), delta H sub f (oxide), electron orbital configuration, and insolubility in Ni.

AbstractUsing a high‐resolution Auger microprobe the chemical structure of the interface in a SiC reinforced titanium alloy has been examined. Only two phases, TiC and Ti5Si3, are identified in the interface. A TiC layer next to the SiC fiber was proven to form a diffusion barrier for titanium. The results aid in the understanding of the fiber surface degradation process during sample production and suggests processes for the further development of these composites.

By ratioing multiple Auger intensities and plotting a two-dimensional occupational scatter diagram while digitally scanning across an area, the number and elemental association of surface phases can be determined. This can prove a useful tool in scanning Auger microscopic analysis of complex materials. The technique is illustrated by results from an anomalous region on the reaction zone of a SiC/Ti–6A1–4V metal matrix composite material. The anomalous region is shown to be a single phase associated with sulphur and phosphorus impurities. Imaging of a selected phase from the ratioed scatter diagram is possible and may be a useful technique for presenting multiple scanning Auger images.

The oxide and diffusion layers produced in a Ni–14Cr–24Al alloy by oxidation in air at 1180 °C for 25 h have been studied using scanning Auger microscopy and ball cratering for depth profiling. During cooling, following oxidation, the oxide layers formed by this alloy spalled profusely. The remaining oxide was very thin (<100 Å) and was primarily Cr2O3 with a trace of Ni (although other oxides are possible). The underlaying metal substrate exhibited γ/γ′ (Ni/Ni3Al) and β (NiAl) phases; however, there was metallic interfacial layer at the surface. This layer was similar to the bulk γ/γ′ phase, but slightly enriched in Cr and Al. These data are compared to electron microprobe results from a nominally identical alloy. The diffusion layer thickness is modeled with a simple mass balance equation and compared to recent results on the diffusion process in NiCrAl alloys.