Aluminum-zirconium alloys exhibit superior strength at elevated temperature in comparison to traditional aluminum casting alloys. These alloys are heat-treatable and their strength depends to a large extent on the quenching and aging steps of the heat treatment process. However, measurements show that the critical cooling rate necessary to retain 0.6 wt. pct. zirconium(the minimum amount necessary for significant strengthening) in a super-saturated solid solution with aluminum is 90ºC/s, which is un-attainable with traditional casting processes. On the other hand, the critical cooling rate necessary to retain 0.4 wt. pct vanadium and 0.1 wt. pct. zirconium in a super- saturated solidsolution with aluminum is only 40ºC/s; which suggests that substituting vanadium for zirconium significantly decreases the critical cooling rate of the alloy. This is an important finding as it means that, unlike the Al-0.6Zr alloy, the Al-0.4V-0.1Zr alloy may be processed into useful components by traditional high pressure die-casting. Moreover, measurements show that the hardness of the Al-0.4V-0.1Zr alloy increases upon aging at 400ºC and does not degrade even after holding the alloy at 300ºC for 100 hours. Also, measurements of the tensile yield strength of the Al-0.4V-0.1Zr alloy at 300ºC show that it is about 3 times higher than that of pure aluminum. This increase in hardness and strength is attributed to precipitation of Al3(Zr,V) particles. Examination of these particles with high resolution transmission electron microscopy (HRTEM) and conventional TEM show that vanadium co-precipitates with zirconium and aluminum and forms spherical particles that have the L12 crystal structure. It also shows that the crystallographic misfit between the precipitate particles and the aluminum matrix is almost eliminated by introducing vanadium into the Al3Zr precipitate and thatthe mean radius of the Al3(Zr,V) particles is in the range from 1nm to 7nm depending on the alloy composition and aging practice. Finally, it is found that adding small amounts of silicon to the Al-0.4V-0.1Zr alloy effectively accelerates formation of the Al3(Zr,V) precipitate.

Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2-4 wt pct. manganese is investigated with focus on the effect of the alloys’ chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy’s yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries

by Kwok Chi-Kong = 氧化鋁及鋁-鈦金屬間化合物增強的鋁基複合物的製造和表徵 / 郭智江. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Kwok Chi-Kong = Yang hua lv ji lü-tai jin shu jian hua he wu zeng qiang de lü ji fu he wu de zhi zao he biao zheng / Guo Zhijiang. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iv / List of tables --- p.v / List of figures --- p.vi / Table of contents --- p.ix / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter 1.1. --- Metal matrix composites (MMCs) --- p.1-1 / Chapter 1.1.1. --- Introduction --- p.1-1 / Chapter 1.1.2. --- Reinforcements in metal-matrix composites --- p.1-1 / Chapter 1.1.3. --- Interface between matrix and reinforcements --- p.1-2 / Chapter 1.2. --- Fabrication of metal matrix composites (MMCs) --- p.1-2 / Chapter 1.2.1. --- Traditional methods --- p.1-2 / Chapter 1.2.1.1. --- Liquid state methods --- p.1-2 / Chapter 1.2.1.2. --- Solid state methods --- p.1-4 / Chapter 1.2.2. --- In-situ methods --- p.1-5 / Chapter 1.3. --- Aluminum based metal matrix composites --- p.1-7 / Chapter 1.4. --- Previous works --- p.1-8 / Chapter 1.5. --- Works in this study --- p.1-9 / Chapter 1.6. --- Thesis layout --- p.1-10 / References / Chapter Chapter 2 --- Methodology and instrumentation --- p.2-1 / Chapter 2.1. --- Powder metallurgy --- p.2-1 / Chapter 2.2. --- Fabrication procedures --- p.2-1 / Chapter 2.3. --- Samples to be studied --- p.2-3 / Chapter 2.4. --- Instrumentation --- p.2-4 / Chapter 2.4.1. --- Differential thermal analyzer (DTA) --- p.2-4 / Chapter 2.4.2. --- Argon tube furnace sintering --- p.2-4 / Chapter 2.4.3. --- X-ray powder diffractometry (XRD) --- p.2-5 / Chapter 2.4.4. --- Scanning electron microscopy (SEM) --- p.2-5 / Chapter 2.4.5. --- Three-point bending test --- p.2-5 / Chapter 2.4.6. --- Arc melting furnace --- p.2-6 / References / Chapter Chapter 3 --- Thermal analysis of Al-Ti02 and Al-Ti02-B203 --- p.3-1 / Chapter 3.1. --- Introduction --- p.3-1 / Chapter 3.2. --- Results and discussions --- p.3-2 / Chapter 3.2.1. --- DTA curve of Al-8.6wt%Ti --- p.3-3 / Chapter 3.2.2. --- DTA curve of Al-12.7wt%Ti02 --- p.3-3 / Chapter 3.2.3. --- DTA curve of Al-12.7wt%Ti02-5.5wt%B203 --- p.3-5 / Chapter 3.2.4. --- DTA curve of Al-12.7wt%Ti02-l lwt%B203 --- p.3-6 / Chapter 3.2.5. --- DTA curve of Al-53.6wt%Ti02 --- p.3-7 / Chapter 3.2.6. --- "DTA curves of Al-12.7wt%Ti02, 22.3wt%Ti02 and 29.7wt%Ti02" --- p.3-7 / Chapter 3.3. --- Conclusions --- p.3-8 / References / Chapter Chapter 4 --- Fabrication and characterization of the Al-Ti02 systems --- p.4-1 / Chapter 4.1. --- Introduction --- p.4-1 / Chapter 4.2. --- Al-12.7wt%Ti02 system --- p.4-2 / Chapter 4.2.1. --- Experiments --- p.4-2 / Chapter 4.2.2. --- Results and discussions --- p.4-3 / Chapter 4.2.2.1. --- XRD spectra --- p.4-3 / Chapter 4.2.2.2. --- Microstructural and composition analyses --- p.4-4 / Chapter 4.2.3. --- Reaction mechanisms --- p.4-6 / Chapter 4.2.4. --- Conclusions --- p.4-8 / Chapter 4.3. --- Al-53.6wt%Ti02 system --- p.4-9 / Chapter 4.3.1. --- Experiments --- p.4-9 / Chapter 4.3.2. --- Sample sintered in tube furnace --- p.4-9 / Chapter 4.3.2.1. --- XRD spectra --- p.4-9 / Chapter 4.3.2.2. --- Microstructural and EDS analyses --- p.4-10 / Chapter 4.3.3. --- Sample prepared by arc-melting method --- p.4-11 / Chapter 4.3.3.1. --- XRD spectra --- p.4-11 / Chapter 4.3.3.2. --- Microstructural and EDS analyses --- p.4-11 / Chapter 4.3.3.3. --- Mechanisms of formation --- p.4-12 / Chapter 4.3.4. --- Conclusions --- p.4-14 / References / Chapter Chapter 5 --- Characterization of the Al-Ti02-B203 systems --- p.5-1 / Chapter 5.1. --- Introduction --- p.5-1 / Chapter 5.2. --- Experiments --- p.5-2 / Chapter 5.3. --- Results and discussions --- p.5-3 / Chapter 5.3.1. --- XRD spectra --- p.5-3 / Chapter 5.3.2. --- Microstructural and composition analyses --- p.5-5 / Chapter 5.3.3. --- Reaction mechanisms --- p.5-6 / Chapter 5.3.4. --- Sample with different contents of B203 --- p.5-7 / Chapter 5.4. --- Conclusions --- p.5-8 / References / Chapter Chapter 6 --- Flexural strengths of the Al-Ti02 and Al-Ti02-B203 systems --- p.6-1 / Chapter 6.1. --- Introduction --- p.6-1 / Chapter 6.2. --- Three-point bending test --- p.6-1 / Chapter 6.2.1. --- Experiments --- p.6-1 / Chapter 6.2.2. --- Results --- p.6-2 / Chapter 6.2.3. --- Discussions --- p.6-3 / Chapter 6.3. --- Conclusions --- p.6-5 / References / Chapter Chapter 7 --- Conclusions and future works --- p.7-1 / Chapter 7.1. --- Conclusions --- p.7-1 / Chapter 7.2. --- Future works --- p.7-2

by Peng Yu. / "Oct. 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / by Peng Yu.

by Ho Man Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Ho Man Wai. / Abstract --- p.i / Acknowledgement --- p.v / Table of Contents --- p.vi / List of Tables --- p.xi / List of Figures --- p.xii / Chapter Chapter 1 --- Intermetallics / Chapter 1.1 --- Background --- p.1-1 / Chapter 1.2 --- Applications of intermetallics --- p.1-4 / Chapter 1.2.1 --- Structural materials --- p.1-4 / Chapter 1.2.2 --- Magnetic materials --- p.1-6 / Chapter 1.2.3 --- Superconducting materials --- p.1-6 / Chapter 1.2.4 --- Hydrogen storage materials --- p.1-7 / Chapter 1.2.5 --- Shape memory alloys --- p.1-7 / Chapter 1.2.6 --- Heating elements --- p.1-8 / Chapter 1.3 --- Prospects of intermetallics --- p.1-8 / References --- p.1-10 / Tables --- p.1-12 / Figures --- p.1-13 / Chapter Chapter 2 --- Metal matrix composites / Chapter 2.1 --- Metal matrix composites --- p.2-1 / Chapter 2.2 --- Conventional fabrication processes of MMCs --- p.2-2 / Chapter 2.2.1 --- Liquid state processes --- p.2-3 / Chapter 2.2.1.1 --- Casting or liquid infiltration --- p.2-3 / Chapter 2.2.1.2 --- Squeeze casting or pressure infiltration --- p.2-3 / Chapter 2.2.2 --- Solid state processes --- p.2-3 / Chapter 2.2.2.1 --- Diffusion bonding --- p.2-3 / Chapter 2.2.2.2 --- Deformation processing --- p.2-4 / Chapter 2.2.2.3 --- Powder processing --- p.2-5 / Chapter 2.2.3 --- In situ process --- p.2-6 / Chapter 2.3 --- Applications of metal matrix composites --- p.2-7 / Chapter 2.3.1 --- Aerospace applications --- p.2-7 / Chapter 2.3.2 --- Non-aerospace applications --- p.2-7 / Chapter 2.3.3 --- Filamentary superconductors --- p.2-7 / References --- p.2-9 / Chapter Chapter 3 --- Molybdenum Aluminide / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- Aluminum --- p.3-1 / Chapter 3.3 --- Molybdenum --- p.3_2 / Chapter 3.4 --- Previous research work --- p.3.3 / Chapter 3.5 --- Present research work --- p.3-4 / Chapter 3.6 --- Thesis layout --- p.3-6 / References --- p.3-8 / Figures --- p.3-9 / Chapter Chapter 4 --- Methodology and Instrumentation / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- Powder metallurgy --- p.4-1 / Chapter 4.3 --- Fabrication methods --- p.4-4 / Chapter 4.3.1 --- Sample preparation --- p.4-4 / Chapter 4.3.1.1 --- Intermetallic samples --- p.4-4 / Chapter 4.3.1.2 --- A1 + Al-Mo composite samples --- p.4-5 / Chapter 4.3.2 --- Cold pressing --- p.4-5 / Chapter 4.3.3 --- Sintering --- p.4-5 / Chapter 4.3.4 --- Arc melting --- p.4-6 / Chapter 4.3.5 --- Hot pressing --- p.4-7 / Chapter 4.4 --- Characterization methods --- p.4-8 / Chapter 4.4.1 --- Thermal analysis --- p.4-8 / Chapter 4.4.1.1 --- Differential Thermal Analyzer (DTA) --- p.4-8 / Chapter 4.4.2 --- Mechanical analysis --- p.4-9 / Chapter 4.4.2.1 --- Tensile Tests --- p.4.9 / Chapter 4.4.2.2 --- Vickers´ةHardness Tests --- p.4-10 / Chapter 4.4.2.3 --- Relative density measurement --- p.4-10 / Chapter 4.4.3 --- Structural analysis --- p.4-12 / Chapter 4.4.3.1 --- Scanning Electron Microscopy (SEM) --- p.4-12 / Chapter 4.4.3.2 --- X-Ray powder Diffractometry (XRD) --- p.4-12 / References --- p.4-13 / Figures --- p.4-14 / Chapter Chapter 5 --- Thermal analysis on the reaction mechanism of the Al-Mo system / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Experimental details --- p.5-2 / Chapter 5.3 --- Results and discussions --- p.5-2 / Chapter 5.3.1 --- "DTA, XRD and SEM analyses of A1 - 57wt% Mo" --- p.5-2 / Chapter (A) --- Temperature < 630°C --- p.5-3 / Chapter (B) --- 630°。C < Temperature < 660°C --- p.5-3 / Chapter (C) --- 660°C < Temperature < 670°。C --- p.5-4 / Chapter (D) --- 670°C < Temperature < 730°C --- p.5-5 / Chapter (E) --- Temperature up to 900°C --- p.5-5 / Chapter (F) --- A brief conclusion --- p.5-6 / Chapter 5.3.2 --- "DTA, XRD and SEM analyses of A1 - 91wt% Mo" --- p.5-6 / Chapter (A) --- Temperature < 630°C --- p.5.7 / Chapter (B) --- 630°。C < Temperature < 660°。C --- p.5-7 / Chapter (C) --- Temperature up to 900°C --- p.5-8 / Chapter 5.4 --- Summary --- p.5-8 / References --- p.5-10 / Tables --- p.5-11 / Figures --- p.5-12 / Chapter Chapter 6 --- Fabrication and characterization of the intermetallic Mo3A18 / Chapter 6.1 --- Introduction --- p.6-1 / Chapter 6.2 --- Experimental details --- p.6-1 / Chapter 6.3 --- Results and discussions --- p.6-2 / Chapter 6.3.1 --- X-ray powder diffraction analysis --- p.6-2 / Chapter 6.3.2 --- Microstructure analysis --- p.6-4 / Chapter 6.3.3 --- "Vickers, hardness measurement" --- p.6-5 / Chapter 6.3.4 --- Relative density measurement --- p.6-7 / Chapter 6.4 --- Summary --- p.6-7 / Figures --- p.6-9 / Chapter Chapter 7 --- Thermal analysis on the formation of the AI-Mo3A18 composites / Chapter 7.1 --- Introduction --- p.7-1 / Chapter 7.2 --- Experimental details --- p.7-2 / Chapter 7.3 --- Results and discussions --- p.7-2 / Chapter 7.3.1 --- DTA and XRD analyses of samples heated up to 700°C --- p.7-3 / Chapter 7.3.2 --- DTA and XRD analyses of samples heated up to 900°C --- p.7-4 / Chapter 7.4 --- Summary --- p.7-6 / Reference --- p.7-7 / Tables --- p.7-8 / Figures --- p.7-9 / Chapter Chapter 8 --- Fabrication and characterization of the A1-Mo3A18 metal matrix composites / Chapter 8.1 --- Introduction --- p.8-1 / Chapter 8.2 --- Experimental details --- p.8-1 / Chapter 8.3 --- Results and discussions --- p.8-2 / Chapter 8.3.1 --- Tensile tests --- p.8-2 / Chapter 8.3.2 --- X-ray powder diffraction analysis --- p.8-5 / Chapter 8.3.3 --- Microstructure analysis --- p.8-6 / Chapter 8.3.4 --- Vickers' hardness measurement --- p.8-7 / Chapter 8.3.5 --- Relative density measurement --- p.8-8 / Chapter 8.4 --- Summary --- p.8-9 / References --- p.8-11 / Figures --- p.8-12 / Chapter Chapter 9 --- Conclusions and future studies / Chapter 9.1 --- Conclusions --- p.9-1 / Chapter 9.2 --- Future studies --- p.9-3

Orientador: Carlos Kiyan / Coorientador: Kratus Ranieri / Banca: Ana Paula Rosifini Alves Claro / Banca: Mirian de Lourdes Noronha Motta Melo / Resumo: A liga AA 356 é uma liga de alumínio de grande importância porque é amplamente utilizada na indústria automobilistica e aeronáutica. Para melhorar as propriedades mecânicas dessa liga, são usados inoculantes para o refino de grãos; essas propriedades, apresentadas pelo produto final, dependem também das condições em que o metal foi fundido e solidificado. Os componentes solidificados em molde de metal, com uma taxa de extração de calor maior, têm propriedades mecânicas superiores àqueles solidificados em moldes de areia, que têm uma taxa de extração de calor mais baixa. A curva de resfriamento é usada como uma ferramenta para avaliar a eficácia de refino de grão e, é influenciada por fatores como o material do molde, a taxa de resfriamento e adições de inoculantes para refino de grão. Com o uso da curva de resfriamento, algumas propriedades da liga podem ser obtidas, tais como: o calor latente de solidificação, a fração sólida, as temperaturas liquidus e solidus, o tempo local de solidificação, além de identificar a presença de inoculantes para o refino de grão. A primeira derivada da curva melhora a precisão das informações apresentadas na curva de resfriamento. Essa derivada representa a taxa de resfriamento. Para o desenvolvimento desse trabalho alguns lingotes foram refundidos variando-se o material do molde e, consequentemente, a taxa de resfriamento; adicionando-se ou não inoculante para o refino de grão na forma de liga mãe Al-5Ti-1B, na proporção de 0,05%. As curvas de resfriamento para as solidificações foram plotadas e analisadas. Confirmou-se que a curva de resfriamento com sua primeira derivada fornecem, além das temperaturas solidus e liquidus, as temperaturas de transformações de fases e informações sobre a eficácia do refino de grão. Variando-se o material... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The AA 356 alloy is an aluminum alloy of great importance because it is widely used in the automobile and aeronautic industries. To improve the mechanical properties of this alloy, inoculants are used for grain refinement; these properties, presented by the final product, also depend on conditions, under which the metal was melted and solidified. The components solidified in a metal mold, with a higher heat extraction rate, have mechanical properties superior to the ones solidified in sand molds that have a lower heat extraction rate. The cooling curve is used as a tool to evaluate the effectiveness of grain refinement and it is influenced by factors as: mold material, cooling rate and of inoculants additions for grain refinement. With the use of the cooling curve analysis can be obtained some properties of the alloy, such as: the latent heat of solidification, the solid fraction, the solidus and liquidus temperatures, the local time of solidification. In addition, to evaluate the presence of inoculants for grain refinement. The first curve derivative improves the accuracy of the information given in the cooling curve. That derivative represents the cooling rate. For this work development, some ingots were remelted varying the mold material and, consequently, the cooling rate; also added or not the grain refinement inoculants in the form of master alloy Al-5Ti-1B, at the rate of 0.05%. Cooling curves for solidifications were plotted and analyzed. It was confirmed that the cooling curve with its first derivative provides, in addition to the liquidus and solidus temperatures, the phase transformation temperatures and information about the effectiveness of grain refinement. Varying the material of molds and through optical microscopy techniques... (Complete abstract click eletronic access below) / Mestre

In this dissertation, the fatigue characteristics of three newly developed experimental compositions for aluminum 7175, with improved mechanical strength, that uses magnesium-calcium alloy instead of pure magnesium are studied. Specimens of each variant were fabricated and subjected to fatigue life testing, fatigue life data analysis, and observation of their fracture characteristics through optical microscopy and scanning electron microscopy (SEM), and metallography to study their grains and surface characteristics. Fatigue life testing shows all three variants have a fatigue strength that is approaching approximately 200 MPa. ECO7175v3 is shown to have the highest fatigue strength of approximately 220 MPa at 5x107 cycles, approximately 40% of its tensile strength of 550 MPa. This is shown by its considerably higher fatigue strength coefficient determined by Basquin's equation compared to the other two variants. ECO7175v1 is shown to generally have large scatter in its fatigue life at higher stress levels (65% or higher of their tensile strength) with coefficient of variations typically twice or more to those of ECO7175v2 and ECO7175v3. The results of the SEM analysis shows that irrespective of the stress levels, ECO7175v1 and ECO7175v3 all have crack initiation points at the surface with no inclusions to act as stress concentrators. The lack of inclusions are supported by the reliability analysis which shows the hazard rates for all variants remains relatively constant the majority of the time before increasing towards the end. These trends for all variants indicates failures are due to wear-outs instead of defects, which were not seen. Reliability analysis also shows that at any given fatigue life cycle and stress level, ECO7175v3 has a lower probability of failure when compared to ECO7175v1 and ECO7175v2. On the other hand, at any given fatigue life cycle and stress level, ECO7175v1 is shown to have a higher probability of failure when compared to ECO7175v2 and ECO7175v3.

Equal channel angular pressing ECAP is a process whereby simple shear is applied to a billet during multiple passages through an angled channel of constant cross section. The process is capable of generating very large plastic strains that significantly refines the microstructure without altering the external dimensions of the billet. A number of properties are influenced by grain refinement with the generation of a submicron grain structure SMG by ECAP resulting in improved strength and hardness and enhanced superplasticity. In this thesis, both an AA7075 alloy and AA7075 Al-base metal matrix composite MMC reinforced with 5 wt. percent of 50 nm diameter SiC particles was produced by a powder metallurgy route followed by hot extrusion. The materials were subsequently deformed by ECAP at 350 C to a true effective strain of 4.6 in an attempt to refine the microstructure and further distribute the SiC reinforcement phase in the composite. The high temperature microstructural stability of both the as-deformed alloy and composite was investigated to elucidate the effect of the reinforcement phase on continuous and discontinuous grain coarsening. It was found that ECAP generated a fine equiaxed grain size of ~ 2.3 !m and ~1.8 !m in the alloy and composite, respectively. The composite was more refined after ECAP since the SiC particles allow the matrix to undergo more grain refinement during deformation. ECAP was found to be a reasonable method for further distributing SiC clusters in this composite which is important for optimizing the reinforcement phase in terms of ambient temperature strengthening and enhanced grain stability at elevated temperature. Both the alloy and composite were annealed at times up to 5h at 500 C to assess grain stability. During annealing, the grain structure of both materials evolved in a continuous manner unlike the discontinuous process of recrystallization. Such a process is similar to continuous recrystallization observed in a range of heavily deformed Al alloys. Substantial grain boundary interactions with MgZn2 precipitates and oxide particles were found in the alloy, with precipitate, oxide and SiC particles found in the composite. The strong pinning force exerted by these particles minimised grain growth in both materials with the composite exhibiting a finer less than 2.5 !m grain size than the alloy less than 3.5 !m after extended annealing. This enhanced grain stability was attributed to the high volume fraction SiC particles which resulted in a large value of the dispersion parameter f/d which results in significant boundary pinning during annealing. Grain stability was also analysed in terms of a recently-proposed mean field model of annealing where it was predicted that the composite should not undergo discontinuous coarsening, as observed experimentally.

This thesis systematically investigates the properties of the aluminium adherend which influence the fracture toughness of aluminium-epoxy adhesive joints in humid environments. The fracture energy of the adhesive joint exposed to a humid environment in comparison with the fracture energy in a dry environment provides a measure of the joint durability. A 500C and 95% relative humidity environment is used to simulate aging of an adhesive joint over several years under normal service conditions. Initially, surface roughness is found to have a significant influence on the fracture toughness of the adhesive joint in humid conditions. A direct correlation between the bond durability and the angle of deliberately machined micro-roughness in the aluminium surface is determined. Consequently a model is developed which initially has the capacity to describe the bond durability performance. The preparation of aluminium surfaces involves the use of a novel ultramilling tool to produce well defined and controlled surface topography. This work represents the first time surface angles of features in the 1????m to 10????m range have been systematically varied and a direct relationship with bond durability has been determined. The use of surface analytical tools aids in elucidating mechanisms involved in the failure of the adhesive joint and contributes to the development of the stress based diffusion model. Examination of the aluminium oxide hydration level reveals this property has a negligible effect on the fracture toughness of the aluminium-epoxy joints exposed to humid environments. This information confirms the dominant role of the physical properties of the aluminium surface in determining the adhesive joint durability. This is the first occasion that planer oxide films grown in an RF plasma have had their hydration state adjusted in a controlled manner and their properties subsequently assessed in terms of bond durability properties. Further alteration of the aluminium surface chemistry is achieved through the application of an organo-silane coupling agent and a series of novel organo-phosphonate compounds. This work further develops the stress based diffusion model developed in conjunction with the micro-machining studies. The components of surface roughness and the ability of interfacial bonds to co-operatively share load are essential for the maintenance of fracture toughness of adhesive joints exposed to humid conditions. The ability of the silane coupling agent to share load through a chemically cross-linked film is a significant property which provides the superior fracture toughness in comparison with the phosphonate treated joints. Although the organo-phosphonate treated aluminium provides hydrolytically more stable bonds than the silane coupling agent, the film is not cross-linked via primary chemical bonds and the reduced load sharing capacity of interfacial bonds increases the bond degradation rate. The stress based diffusion model evolving from the initial work in the thesis can be used to predict the performance of more complex systems based on a thorough characterisation of the aluminium surface chemistry and topography. The stress based diffusion model essentially describes the concept of the production of micro-cavities at the epoxy-aluminium interface under mode 1 load, as a result of the distribution of strong and weak adhesive bonds. Alternatively, micro-cavities may result from an inhomogeneous stress distribution. In areas where the adhesive bonds are weak, or the local stresses are high, the interfacial load produces larger micro-cavities which provide a path of low resistance for water to diffuse along the bond-line. The water then degrades the adhesive bond either through the displacement of interfacial epoxy bonds or the hydration of the oxide to form a weak barrier layer through which fracture can occur. Alternatively, the water can hydrolyse the adhesive in the interfacial region, leading to cohesive failure of the epoxy resin. The bond durability performance of a series of complex hydrated oxide films used to pre-treat the aluminium adherend provides support for the stress based diffusion model. Whilst surface area is an important property of the aluminium adherend in producing durable bonding, the best durability achievable, between an epoxy adhesive and aluminium substrate, requires a component of surface roughness which enhances the load sharing capability in the interfacial bonding region. This component of durability performance is predicted by the model. In more specific terms, a boiling water treatment of the aluminium adherend indicates a direct correlation between bond durability, surface area and topography. The characterisation of film properties indicates that the film chemistry does not change as a function of treatment conditions, however, the film topography and surface area does. The overall bond durability performance is linked to both of these properties. The detailed examination of the hydrated oxide film, produced by the boiling water treatment of aluminium, is the first time the bond durability performance has been related to the film topography. It is also the first occasion that the mechanism of film growth has been examined over such a large treatment time. The combination of surface analysis and bond durability measurements is invaluable in confirming the properties, predicted by the stress based diffusion model, which are responsible in forming fracture resistant adhesive bonds in humid conditions. The bond durability of high surface area and low surface area hydrated oxide films indicates that surface area is an important property. However, this study confirms that the absence of the preferred surface topography limits the ultimate bond durability performance attainable. The fracture toughness measurements performed on aluminium adherends pre-treated with a low surface area film also supports the mechanism of load sharing of interfacial adhesive bonds and its contribution to the overall bond durability. The role performed by the individual molecules and particles in an oxide film is similar to the load sharing performed by the silane coupling agent molecules. Further support for the stress based diffusion model is provided by films produced on aluminium immersed in nickel salt solutions. The topography of these film alters as a function of treatment time and this is directly related to fracture toughness in humid environments. This work provides the first instance where such films have been characterised in detail and their properties related to bond durability performance. The study is also the first time that the growth mechanism of the film produced on the aluminium substrate has been examined in detail. The film growth mechanism supports the film growth model proposed for the hydrated oxide film produced by the boiling water treatment. The major findings presented in this thesis are summarised as the direct correlation between surface profile angle, the importance of co-operative load sharing of interfacial adhesive bonds and the relative insignificance of surface oxide hydration in the formation of durable aluminium-epoxy adhesion. This information is used to develop a stress based diffusion model which has the capacity to describe the fracture toughness of a range of aluminium-epoxy adhesive joint systems in humid environments. The stress based diffusion model is also capable of predicting the relative performance of the bond systems examined in the final chapters of the thesis, where complex interfacial oxide films are involved in the formation of adhesive bonds.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.