The application of chemical state AES and SAM to the examination of spray‐formed aluminium alloy fracture surfaces

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Abstract
The fracture surface of a spray‐formed Al‐5.2Cr‐1.4Zr alloy has been examined using AES and scanning Auger microscopy (SAM). Cratered regions of the surface were identified and high‐energy resolution AES analysis showed a localized 20 Å thick Al2O3 film to be present in these areas. Chemical‐state imaging of the Al fracture surface enabled the local distribution of oxide to be determined. The surface topography was not found to be suppressed using the standard (PB)/B or (PB)/(P + B) correction algorithms. This point is discussed with consideration of the electron emission from such highly structured surfaces. The oxide thickness measured from the craters is in good agreement with that previously determined by XPS for powder particles produced in the atomization process. Crater formation is suggested to occur as a result of complete powder particle solidification prior to the particles impacting the substrate/deposit. The localized oxide, revealed by fracture, presents areas of weakness in the unworked material.