The fracture properties of a series of alloys containing 15% chromium and 0.8 to 3.4% carbon are investigated using strain fracture toughness testing techniques. The object of the work is to apply a quantitative method of measuring toughness to abrasion resistant materials, which have previously been assessed on an empirical basis; and to examine the relationship between microstructure and K10 in an attempt to improve the toughness of inherently brittle materials. A review of the relevant literature includes discussion of the background to the alloy series under investigation, a survey of the development of fracture mechanics and the emergence of K10 as a toughness parameter. Metallurgical variables such as composition, heat treatment, grain size, and hot working are used to relate microstructure to toughness, and fractographic evidence is used to substantiate the findings. The results are applied to a model correlating ductile fracture with plastic strain instability, and the nucleation of voids. Strain induced martensite formation in austenitic structures is analysed in terms of the plastic energy dissipation mechanisms operating at the crack tip. Emphasis is placed on the lower carbon alloys in the series, and a composition put forward to optimise wear resistance and toughness. The properties of established competitive materials are compared to the proposed alloy on a toughness and cost basis.

The frequency variations of attenuation and phase lag of the modulated gas flow through thin metal foils have characteristic features whether permeation is diffusion controlled, is influenced by surface reactions or affected by interna1 trapping. Analysis of data obtained for hydrogen permeation through nickel show that hydrogen is dissociatively chemisorbed in nickel. The permeation parameters diffusivity, permeability and surface reaction rate obtained for nickel are: D/(m²s-1) = 7.12 x 1-7 exp [-4.64 x 103/RT/(K)] Pm/(molH₂m⁻¹s⁻¹Pa⁻¹/² = 3.35 x 10⁻⁷ exp[-54.25 x 10³/RT/(K)] Ksm/(molH₂m⁻³Pa⁻¹/²) = 0.47 exp[-13.6 x 10³/RT/(K)] K₁/(molH₂m⁻²s⁻¹Pa⁻¹) = 1.44 x 1⁻⁶ exp[-29.68 x 10³/RT/(K)] where R=8314Jmol⁻¹. The experiments conducted on cold-worked nickel have revealed that hydrogen is trapped within the bulk during the permeation in this material. A series of experiments conducted on cold worked nickel+2% thoria has also revealed that hydrogen is trapped within the bulk during the permeation. Analysis of data obtained for cold worked nickel+2% thoria suggest that hydrogen is trapped at the dislocation networks around thoria particles. Frequency variation of attenuation and phase lag of the modulated flow show that hydrogen trapping in both cold-worked nickel and nickel+2% thoria is in dynamic equilibrium. A trap depth of 40 kJ/mol has been obtained for nickel+2% thoria.

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An investigation into the active species in iron-catalysed Kumada-type reactions of mesitylmagnesium bromide in the presence of stoichiometric TMEDA revealed that the anion [Fe{meshr is the only observable paramagnetic species under the reaction conditions. It had previously been reported that the neutral adduct [Fe{mesh{TMEDA)) was an on-cycle intermediate that reacted with the electrophile; however, the anionic species was shown to react faster with electrophiles allowing the catalytic cycle accepted in the literature to be revised. When the reactions of less-bulky aryl Grignard reagents were studied, oxidation states below Fe(lI) were accessed as soluble Fe(l) complexes or suspensions of Fe{O) nanoparticles. This suggests different manifolds are in operation depending on the steric properties of the nucleophile and a general catalytic cycle is likely invalid. A range of iron-phosphine complexes was investigated as alternative catalysts in the Suzukitype cross-coupling of tetraarylborates in the presence of sub-stoichiometric diaryl zinc species. The coupling reactions of more synthetically expedient aryl trialkylborates formed from commercially available starting materials with benzyl halides were developed. The iron-catalysed cross-coupling reactions of related aryl nucleophiles of aluminium, indium, gallium and thallium with alkyl, benzyl and allyl halides were achieved using a commercially available iron pre-catalyst. Fe(l) was shown to be a kinetically accessible oxidation state under catalytic conditions, and complexes of the form [FeX(dpbzhJ (X = CI, 4-tolyl) were formed using all the relevant nucleophiles. Iron-catalysed cross-coupling reactions using 'soft' nucleophiles have previously required the use of expensive or synthetically challenging bisphosphines based on the orthophenylene backbone. The development of "pre-reduction" conditions allowed a range of state-of-the-art coupling reactions to be performed using pre-catalysts based on the cheap and readily ava ilable bisphosphine 1,2-bis(diphenylphosphino)ethane. Mechanistic investigations revealed the importance of Fe(l) complexes as active species, with the loss of a ligand from the catalytic resting state [FeCI(dppehJ likely to occur prior to rate determining oxidative addition.

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