Browsing by Author "Scenini, Fabio"

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    Metallographic Characterisation of Cold Worked Type 304 Austenitic Stainless Steels
    (Materials Performance Centre, University of Manchester, 2007-09) Ahmed, Ismaila Idowu; Scenini, Fabio; Sherry, Andrew H.
    The influence of cold work on the Stress Corrosion Cracking (SCC) susceptibility of Austenitic Stainless Steels (ASS) is an ongoing topic of research. While some workers have suggested that low levels of cold work are deleterious to SCC, others argue that high levels may be favourable to SCC under certain conditions. The objective of this report is to quantify a number of key parameters associated with the influence of cold work on SCC susceptibility. The microstructures of ASS subjected to different deformation modes and different levels of cold work have been examined using a range of techniques: optical metallography was carried out to determine the grain size and elongation ratio; the X-ray diffraction technique was used to quantify the amount of strain- induced martensite and residual stress; and lastly, deformation texture was examined using Electron Back Scatter Diffraction (EBSD) technique. In addition, Vickers hardness was used to quantify the material hardness in each condition of cold work. The outcome of the characterisation showed that the Vickers hardness and the volume fraction of strain induced martensite increases with both increasing levels of cold work and weight percent of carbon in the material composition. The stability of delta ferrite was also affected by the proportion of ferrite-stabilising elements (e.g. Si) in the composition. Bi-rolling (i.e. cross- rolling) significantly increased the hardness value and the amount of strain induced martensite compared with samples in which cold work was generated either by uniaxial rolling and pulling (i.e. tensile cycling). Cross-rolling also led to a more uniform distribution of delta-ferrite within the microstructure than either unidirectional rolling or pulling.