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Abstract:A surface preparation route is presented that is designed to give high-quality finishes to austenitic stainless steels for analysis with advanced scanning probe microscopy techniques. The method details a series of polishing and cleaning steps suitable for novices and experts alike. The steps taken are justified throughout and illustrated with examples of potential defects.

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms MALDI, colloidal graphite, matrix suppression, small molecules, matrix. AbstractThe analysis of low molecular weight compounds by Matrix-Assisted Laser Desorption/Ionisation mass spectrometry is problematic due to the interference and suppression of analyte ionisation by the matrices typically employed -which are themselves low molecular weight compounds. The application of colloidal graphite is demonstrated here as an easy to use matrix that can promote the ionisation of a wide range of analytes including low molecular weight organic compounds, complex natural products and inorganic complexes. Analyte ionisation with colloidal graphite is compared with traditional organic matrices along with various other sources of graphite (e.g. graphite rods and charcoal pencils). Factors such as ease of application, spectra reproducibility, spot longevity, spot-to-spot reproducibility and spot homogeneity (through single spot imaging) are explored. For some analytes considerable matrix suppression effects are observed resulting in spectra completely devoid of matrix ions. We also report the observation of radical molecular ions [M -• ] in the negative ion mode, particularly with some aromatic analytes.

In this study, the evolution of sigma-phase development in a 2205 duplex steel was studied following thermal ageing in the temperature range 750-850°C for periods up to 100 h. A suite of materials analysis techniques including combined electron backscatter diffraction-energy-dispersive X-ray imaging and magnetic force microscopy are used to quantify the change in volume fraction of the phases. The experimental results for each ageing condition are compared with the results from other ageing experiments and the predictions from the computer modelling. They show good correlation for the amount of sigma phase formed under a range of ageing conditions (and thus varying quantities of sigma phase). EBSD measurements showed no preferential orientation relationships relative to the parent ferrite for the nucleation of sigma phase, implying that the minimisation of boundary misorientation energy is not significant in determining sigma-phase nucleation sites. The results are discussed with respect to the experimentally measured properties of sigma phase and the kinetics of the precipitation process.

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A Type 316H austenitic stainless steel component containing Cr and impurity element-rich localised regions arising from component fabrication was aged for a prolonged period during service at a temperature of approximately 550°C. These regions make up approximately 5% of the total volume of the microstructure. Previous work has shown that these regions contain ferrite and carbide precipitates and a finer austenite grain size than the adjacent matrix. The present study has used high-resolution transmission electron microscopy combined with compositional microanalysis to show that these regions have a highly complex microstructure containing G phase, chi phase and intragranular c 0 precipitates within the austenite grains. There is phosphorus migration to the chi austenite phase boundary, and the basis for this equilibrium impurity segregation is discussed. A Cr-depleted region was observed surrounding the chi phase precipitates, and the impact of this on the other precipitates is considered. The diversity of precipitates in these Cr-rich regions means that they behave significantly differently to the bulk material under long-term creep conditions leading to preferred nucleation and growth of creep cavities and the formation of localised creep cracks during service.