Two distinct techniques for “optimum” fibre spreading of 2400 Tex E-glass and 12K carbon fibre bundles were designed and developed in this research project. These techniques enabled increases in fibre bundle width of 956% and 1121% for E-glass and carbon fibre bundles respectively. These values surpass anything reported in the literature. Tensile testing was conducted on dry fibre bundles in the as-received and spread state. A reduction in the tensile failure stress and Weibull survival probability was observed with an increase in gauge length. The effect of spreading was determined to be statistically significant at a gauge length of 100 mm; however it was not significant at a gauge length of 50 mm. Composites were manufactured using as-received or spread fibre bundles and their properties analysed and compared. The composites manufactured using spread fibre bundles were significantly thinner than those manufactured using as-received fibre bundles. In hybrid composites the degree of mixing of the two reinforcing fibre types was greater than has been reported in the literature. The overall conclusion from this study is that the utilisation of spread E-glass and carbon fibre bundles can be used as a means for enhancing the apparent failure strain of carbon fibre composites.

The susceptibility of Ti6246 to cold dwell fatigue behaviour has been assessed as part of a wider investigation into the relationship between optical microstructure, crystallographic texture, mechanical behaviour and material processing for various common titanium aerospace alloys. Assessment of the full range of production microstructures for Ti6246 has shown acceptable maximum texture intensities and crystallographic unit size variations. Debit on cold dwell fatigue life has only been observed at very high proportions of the ultimate tensile strength of the material. Heat treatment to eliminate potential ‘good’ factors in the dwell response of conventional microstructures was also noted not to produce a large cold dwell fatigue life debit. The absence of dwell effects may be attributed to one or more factors, including susceptibility of large colony microstructures to other failure modes to the extent that they are activated before the mechanism leading to cold dwell fatigue facet formation. Characterisation of optical microstructures and textures has revealed a range of structures associated with different titanium alloys and product forms. It has been noted that common crystallographic features may be observed in very different microstructures in these alloys. It is concluded from this work that the optical microstructure should not be taken as an accurate indication of the effective structural unit size in titanium alloys.

Despite of the wide application of zirconium and its alloys, wear and corrosion of zirconium components are major issues for demanding applications. To this end, ceramic conversion (CC) treatments at different temperatures for varying time were therefore carried out on both Zr702 and Zircaloy-4 alloys. In addition, first trial of duplex surface treatment was conducted on Zr702 alloy to study the response of the CC formed ceramic layer to oxygen boost diffusion (OBD) and to increase the oxygen diffusion zone (ODZ). Results showed increased anti-corrosion and anti-wear properties due to the generation of dense ceramic layer (mainly m-ZrO\(_2\) and t-ZrO\(_2\)) supported by a hardened diffusion zone on the surface. Pitting corrosion of as received Zr702 and Zircaloy-4 can be eliminated; improvement in wear resistance at best treatment condition has increased 3.7×103 and 8.9×102 times for Zr702 (530°C/10hrs) and Zircaloy-4 (500°C/10hrs) respectively. The main wear mechanism has changed from adhesive wear for the as-received materials to mild abrasive wear of the CC treated samples. OBD treatment in both two-step and three-step duplex surface treatments can further increase the wear performance of Zr702 due to the reduced porosity and cracks in the oxide layer and thickened oxygen diffusion zone.

The dwell fatigue crack growth behaviour of coarse grained RR1000 has been studied using advanced mechanical testing and characterization techniques. Crack growth under sustained loading has also been considered. Environmentally enhanced crack growth at high temperatures in air follows a stress assisted grain boundary oxidation (SAGBO) mechanism, with a 100-300 nm long Al2O3 intrusion ahead of the crack tip. When its thickness of reaches a critical value, this intrusion fails and crack advance ensues. The crack growth process is discontinuous and highly uneven. The dwell fatigue/sustained loading crack growth rates are affected by the stress relaxation ability of the materials, which is related to the size and distribution of tertiary γ' precipitates, testing temperature and stress state. Oxidation damage is deduced to be a dominant factor affecting crack growth over a range of temperature from 600 to 700 °C. At 700 °C oxidation damage begins to have an effect on fatigue crack growth at a dwell time of 30 s. Creep damage is suggested to make the dominant contribution to crack growth at 750 and 775 °C both in air and in vacuum.

Boron addition has been used to refine the microstructures in TiAl castings, such as LPT blades, to improve ductility. However, boride precipitates with undesired morphologies could reduce ductility and even wipe out the entire benefit from grain refinement. Boride morphology in Ti45Al2Mn2Nb1B was found to be closely related to solidification conditions and proper processing windows have been established. In order to improve temperature capability of cast TiAl alloys to cater for the demand in new engines TiAl alloys have to be alloyed with more refractory elements, such as Nb and Ta, which will inevitably affect the boride morphologies. In this study variant alloys based on Ti45Al2Mn2Nb1B have been investigated with emphasis on the relationship between boride morphology, alloying element species and cooling conditions and distinctly different boride formation behaviour in different alloys was observed. In addition, curvy borides were found both on the fracture surface and within the microstructure in tensile test pieces, especially in Hf-containing test pieces, which indicate that curvy borides have the strongest effect in reducing ductility regardless of alloy composition.

This thesis is an investigation into a family of features that can form during the inertia friction welding of the nickel-based superalloy RR1000. A thorough characterisation of the weld features using scanning-electron microscopy has been carried out, yielding information about their composition, microstructure, morphology and their distribution within the weld zone.

The object of the work described is to determine whether, in any nickel compound, the paramagnetism of the nickel is approximately neutralised by the diamagnetism of the molecule, so that it might be possible to change the sign of the susceptibility by temperature change alone. A method for measuring small susceptibilities has been developed which, in comparison with current methods, uses simpler apparatus, and simplifies the taking of observations, without prejudice to accuracy or sensitivity. The susceptibilities of a number of nickel compounds have been investigated. It is found that the susceptibility is profoundly affected by the nature of the chemical valence link. In polar compounds the nickel retains a practically constant paramagnetism which is considerably larger than the underlying diamagnetism, and it is hence concluded that such compounds are unsuitable for investigations of change of sign of susceptibility by change of temperature alone. It is suggested that the investigation might be carried out on certain nickel dioxime compounds. The results indicate an abnormality in the structure of nickel cyanide.

This research takes the principle of localised heat treatment using inert gas jets from concept to delivery of a working prototype system and its application on a specific component. Described is the development of this technology and proof of its thermal capabilities on a number of components and test pieces. Included are discussions on the atmospheric requirements of the system and the development of the system design to minimise the formation of significant oxidation and alpha case. Finally the later sections of this thesis detail the work carried out to understand the underlying principles of this technology and how this understanding can be read across to future applications. This is done in the form of process modelling; the output of this being boundary conditions which can be used to model this technology for a number of applications and geometries in the future.

During wet-filament winding, fibre bundles are impregnated using a drum-based resin bath. The impregnated bundles are then directed to a traversing-arm prior to being over-wound onto a rotating mandrel. Once the required number of layers of the impregnated fibres has been deposited on the mandrel, the assembly is transferred to an oven to cure the thermosetting resin. After this, the composite is cooled to ambient temperature and extracted from the mandrel. There are a number of issues with the conventional manufacturing method including the generation of waste resin, utilisation of significant volumes of solvent for cleaning the equipment at the end of each shift, contamination of the factory floor due to resin drips from the impregnated tows and the cost of waste disposal. This thesis reports on the integration of a modified wet-filament winding process, which is referred to as "clean fi lament winding", into an industrial filament winding manufacturing operation. It was demonstrated that the clean filament can be utilised to address the above-mentioned issues associated with the conventional wet-filament winding. For example, an 88.12% and 87.5% reduction in solvent consumption and the generation of waste resin respectively was verified when compared to conventional wet-filament winding. Hence, it can be concluded that the clean filament winding technique is capable of producing industrially relevant filament wound composites with marginally superior or equivalent properties when compared to conventional wet-filament winding. However, the environmental benefits of the clean filament winding technique are significant.

This study, completed with the University of Birmingham, was sponsored by Controls and Data Services (CDS) and the Engineering and Physical Sciences Research Council (EPSRC). A range of materials and processes were evaluated with the aim of producing a lead-free, monolithic, machinable plain bearing to replace the leaded bronze gear pump bearings currently used. The primary alloys investigated in this thesis were Al-20Sn-7Si-1Cu and an Al-20Sn-7Si- 1Cu-1Mg wt% composition; with the latter achieved by the controlled addition of Al- 50Mg wt% master alloy. The project identified an aluminium-tin-silicon based alloy that could be sintered to near 100% of theoretical density in the manufacture of a ¾ scale rod form. The process and material produced should be capable of replacing the bearing alloys typically used in aerospace pump applications. The addition of magnesium, with controlled morphology and size, and the parallel use of a nitrogen sintering atmosphere, significantly improved the heat treated density of these materials. Successful sintering, typically completed at 500°C, could be significantly reduced in time by the use of pressurised nitrogen from 20 hours to 5 hours. The sintered microstructure generated was a heat treatable aluminium / copper matrix with desirable, discrete regions of silicon (typically 3 – 4 microns in size) and reticular tin.