Wide area beam averaged AEM of precipitate particles extracted on replicas from Type 316 stainless steel

Extraction replicas are an important complement to in-foil analysis for accurate phase identification and composition measurements in studying precipitation in complex alloys such as Type 316 stainless steel. Analysis of small particles without matrix interference is particularly easy on replicas. Background or in-hole counts on clean replicas are very low compared to in-foil. This is important for reactor-irradiated materials where intrinsic radioactivity emission interferes with or obscures x-ray detection in-foil. This work introduces another advantage of replicas by demonstrating an analysis in which a wide area beam is used to blend spectra from many particles into a composite averaged spectrum. Such an averaged spectrum better represents the elemental redistribution from the original matrix to the precipitate microstructure and can yield relative phase fractions upon deconvolution if the individual phase compositions are known. This work compares two precipitate microstructures in one heat of 20%-cold-worked (CW) Type 316 stainless steel, one produced by aging for 10,000 h at 6500C, the other by EBR-II irradiation to 36 dpa at 6300C. Quantitative compositional analyses for the irradiated specimens are given