Effects of cold work on material properties for high temperature fastener materials

This project will involve extensive material property evaluation including creep, stress relaxation, slow strain rate tensile tests, oxidation, total fatigue life, fatigue crack growth resistance and notched stress rupture tests. Advanced material characterisation techniques will include EBSD and analytical TEM and SEM. Overall the programme will contribute to defining an operating envelope for the cold worked material and to rationalise the choice of cold-worked or non-cold worked material for specific applications. Areas to be explored for cold worked material are expected to include a consideration of phase stability, environmental susceptibility, crack initiation life, notch- brittleness, crack growth rates and stress relaxation rates- all at elevated temperatures. Results will be correlated with underlying microstructural features to be characterised in detail throughout the programme. The behaviour of cold- worked materials at high temperatures is not well understood and the project will contribute to fundamental understanding of this topic, together with some specific attention to issues focused on their use as fasteners.