This research explores the relative merits of existing and novel ultra-hard tool materials for finish turning titanium alloys. Phase 1 of the experimental work comprised evaluating the machinability of Ti-6Al-2Sn-4Zr-6Mo when employing carbide tooling with respect to tool life, wear behaviour, workpiece surface integrity and cutting forces. The machinability of Ti-6Al-2Sn-4Zr-6Mo using PCBN tooling was evaluated in Phase 2 experiments. It was shown that even with the use of high pressure jet cooling, carbide and low content PCBN grade inserts were unsuitable for high-speed (~200 m/min) finish turning of titanium alloys. Phase 3 research evaluated the machinability of Ti-6Al-2Sn-4Zr-6Mo and Ti-6Al-4V when employing PCD tooling with respect to tool life, wear behaviour, workpiece surface integrity and cutting forces. Benchmark tests producing response surface models were developed using conventional low pressure fluid supply and were found to be suitable for the prediction of tool life, surface roughness and cutting force within the range of parameters studied. The PCD inserts significantly outperformed both carbide (by a factor > 24) and PCBN (by a factor > 12) tools in high-speed finish turning, although the performance varied depending on the PCD structure, edge geometry, period of engagement, undeformed chip thickness and jet fluid parameters.

A ternary system of Cahn-Hilliard equations is used to model phase separation processes in bimetallic nanoparticles. The third component in the ternary system is taken to be vacuum, such that we are able to simulate bimetallic nanoparticles without any need to impose restrictions on the nanoparticle boundary. Strain effects, due to lattice mismatch, are introduced by coupling with the Navier-Lamé equations. The use of this diffuse-interface approach allows the simulation of significantly larger systems than currently feasible with atomistic methods. Particular attention is paid to the core-shell to quasi-Janus particle transition that has been observed in CuAg and other bimetallic nanoparticles of weakly miscible elements. Our simulations are able to capture the various effects seen previously in experimental work and in atomistic simulations. In particular, we observe a transition from core-shell structure to quasi-Janus particle structure as the size of the particles increases. Moreover, it is shown that core-shell particles prevail when the thickness of the shell is small in comparison to the core size. The inclusion of elastic effects into the model further promotes the formation of quasi-Janus particles. The transition from core-shell to quasi-Janus particle structure is, however, also seen in the absence of elastic effects.

The development of flexible pipelines and risers has been a key driver in allowing the oil and gas industry to develop fields in deeper and deeper waters, utilising floating production technologies. During service, the annulus environment located between the two polymer layers of the pipe may become corrosive. Permeation of corrosive species from the produced fluids along with permeation and subsequent condensation of water in the annulus of the pipe may result in the development of an acidic aqueous environment. If this situation occurs in service the integrity of the carbon steel tensile armour wires located in the annulus may be at risk. As such, it is the aim of the current research project to investigate the effect of simulated corrosive oilfield environments on the fatigue life of the tensile armour wire component of the pipe.

Precipitation hardening Ni based superalloys have been widely used in gas turbine engine components owing to their stable microstructure at high temperature. To assemble these components, joining technology is necessary and friction welding is used for the joints which are suitable for large component welding, taking advantage of its superior mechanical properties compared to fusion welding. Inertia friction welded RR1000 and Inconel718 microstructure was studied. In this study, grain boundaries were intensively characterized to rationalize the intergranular susceptible area from the microstructure point of view.

Aluminium powder metallurgy provides lightweight automobile components for reduced energy consumption. Conventional press-and-sinter methods can leave porosity in final parts, which reduces strength of the alloy. Equal Channel Angular Pressing (ECAP) can be used to increase density of powder compacts after sintering via severe plastic deformation. Solid state sintering of pure aluminium and liquid phase sintering of a commercial Al-Sn bearing alloy were analysed with industrial collaborative support. The use of room temperature ECAP to these sintered materials was investigated. Cold compaction produced a porous region on the outside of all samples due to increased friction at the die wall. The application of ECAP to pure aluminium and bearing alloys caused elongation in the longitudinal section and a relatively equiaxed microstructure in the transverse section. Sintering at 500°C for 1 and lOhours and 550°C for lh was ineffective as liquid tin did not wet the aluminium effectively. After ECAP, density and hardness increased with refined grain sizes and formed two distinct regions; a denser, deformed core and a non-deformed skin, which resulted from non-uniform densification after cold compaction.

The work in this thesis aims to investigate the ductility of s-HD (solid hydrogenation disproportionation) processed book mould cast NdFeB material in order to develop a novel processing route for producing fully dense magnetic material with a high energy product. A major drawback of NdFeB–based alloys is that they are extremely brittle. Therefore, to produce a fully dense magnet these alloys must be broken down into a powder and hot pressed or sintered followed by cutting and grinding to the desired shape and precise dimensions. This process is time consuming, energy intensive and produces a significant amount of waste which is not readily recyclable. This thesis reports a potentially new application of hydrogen as a promising high temperature processing tool in which the normally brittle Nd\(_2\)Fe\(_1\)\(_4\)B based intermetallic absorbs and reacts with hydrogen, converting it into a ductile, disproportionated condition, which can be subsequently compressed at room temperature. It can then be restored to its original state by removal of the hydrogen under partial vacuum at elevated temperatures. By maintaining a solid form throughout, almost zero waste material is produced and the deformed material exhibits a high coercivity and a useful degree of anisotropy.

Surface damage can be introduced into rotor disc components during assembly, maintenance and overhaul operations for aircraft engines. This is known as handling damage and is often in the form of surface scratches, which are known to reduce total component fatigue life. This work provides a holistic understanding of the effect of artificial scratch damage on the fatigue performance of a nickel-based superalloy used for compressor and turbine disc applications. Following extensive analysis of results from previous test programmes completed at Rolls Royce plc., a series of low cycle fatigue tests were performed on Alloy 720Li specimens. A test matrix was designed to isolate and identify every factor that may contribute to the fatigue properties of scratch damaged components. The geometry of a scratch, which causes a local stress concentration and increases the ‘effective Kt’ at the scratch root, is the most significant factor in controlling fatigue performance. Scratches cause a decrease in crack initiation life, thereby reducing total component fatigue life. Compressive residual stresses induced by shot peening and the scratching process itself are beneficial to component life. Varying levels of scratch damage were fully characterised by scanning electron microscopy, microhardness testing and electron backscatter diffraction to show the severe microstructural modification and increased hardness caused by the scratching process. Computational modelling was carried out to determine geometrical effects of scratches on local stress and strain fields. The ‘effective Kt’ values under scratches were calculated, which helps to predict fatigue performance. This type of comprehensive investigation is important for damage tolerance lifing approaches and helps to minimise premature component retirement.

Field Assisted Sintering Technique (FAST) was used for the crystallisation of ionomer glasses and the production of the relevant glass ceramics. Extrusion was also used as an alternative processing method to produce honeycomb glass ceramics derived from similar glass compositions. Apatite-mullite glass ceramics derived from the general glass composition 4.5SiO\(_2\)-3A1\(_2\)O\(_3\)- 1.5P\(_2\)O\(_5\)-(5-x)CaO-xCaF\(_2\) can be produced by a lost wax method. However, Field Assisted Sintering Technique and Honeycomb Extrusion Technique are never used before and this present work presents the first data on the use of both of the above mentioned techniques. Calcium (Ca), Strontium (Sr) and Magnisium (Mg) containing glass powder compositions were produced and processed by FAST and Extrusion technique. X-ray diffraction of the materials produced by FAST showed the formation of a fluorapatite, mulite and a minor A1PO\(_4\) phase for the calcium glass. Sr-fluorapatite and Sr-aluminium silicate were formed in Sr glass and mullite and wagnerite were formed in Mg glasses. All the crystal phases formed were in good agreement with previous conventional crystallization studies. The FAST sintered glass ceramic properties were improved when compared with conventional sintering. In extrusion technique, the rheological properties were studied using Benow/Bridgwater model for paste parameters. Honeycomb extrusion pressure drop was also studied using a model developed by Blackburn and Bohm. In this study, we used waste glass to model the binder rehology of glass powder and modelled binder rheology in the apatite mullite glass. The measured paste parameters were in good agreement when compared with the experimental results. The produced honeycomb structure was sintered conventionally using a furnace. Microstructural studies and X-ray diffraction were carried out. The results of this studies show a well-defined porous structure and formation of crystal phases similar to the phases observed during conventional sintering.

This thesis is concerned with the fabrication and characterisation of lead free piezocomposites and transducers for use in high frequency medical ultrasound imaging applications. A water based gel casting and micro moulding approach has been developed to fabricate 1-3 composites with a random pillar structure in the lead free and lead based piezoelectric material. High frequency transducers incorporating the random composites as the active components have been fabricated, characterised and demonstrated in real tissue imaging environments. A water based gel casting system has been used incorporating Hydantoin Epoxy resin, amine hardener (Bis (3-aminoproply) amine) and dispersant. Viscosities of the 50BCZT and PZT systems were minimised by the addition of 2.4 and 1 wt% of dispersant respectively. The highest values of piezoelectric and dielectric properties corresponded to 50BCZT samples fabricated with a gel casting slurry incorporating 30 wt% resin and sintered at 1425 °C, with d33 and kp values of 330 pC/N and 0.43, respectively. 1-3 composites were successfully fabricated from the BCZT and PZT bristle block structures and only one resonance peak corresponding to the thickness mode was observed. PZT composites offered generally higher thickness coupling coefficients than 50BCZT composites, where the highest value of 0.78 was measured for samples sintered at temperature 1425 °C. Focused PZT, focused 50BCZT, unfocussed PZT and unfocussed 50BCZT transducers were successfully fabricated using the composites with randomised structure, and have operating frequencies of 35, 40, 50 and 35 MHz respectively.

The atmospheric corrosion of 304L and 3 16L austenitic stainless steels was investigated in conditions relevant to the storage of intermediate level nuclear waste (I L W). Thin electrolyte films were created via automated droplet deposition, allowing multiple tests to be conducted in parallel. In-situ monitoring of droplet arrays on stainless steel samples was conducted with the use of a flat-bed document scanner, allowing large-scale, automated monitoring of corrosion processes. The initiation time for individual corrosion processes was established, showing that corrosion was slower to initiate under less aggressive conditions, and allowing 'true corrosion site lifetimes to be recorded, and compared with their depths. The presence of precipitated species within an electrolyte film was shown to affect the corrosion processes within that film. Both NaCl precipitates and glass shards acted as barriers to ion transport. This affected both the propagation of corrosion, and the electrochemical potential within the droplets; a higher precipitate content decreased the average corrosion depth and the extent of corrosion. The presence of nitrate and sulphate salts, both known corrosion inhibitors in full- immersion conditions, was shown to inhibit atmospheric corrosion when the inhibitor:chloride ratio was above a certain value. This was independent of the absolute amounts of salts, but dependent on the exposure humidity of the test.