A focused ion beam coupled with electron backscatter diffraction was used to reconstruct high-resolution three-dimensional features at silica particles in a cold-rolled and annealed nickel crystal. ...It was found that cold rolling to a true strain of ∼0.92 generated a pair of crescent-shaped voids at every particle in the analyzed volume. Both the location and shape of these voids at each particle was found to be related the position of the particle deformation zones and nucleation sites during subsequent recrystallization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Texture and microstructure development during hot plane strain compression of Al–6Cu–0.4Zr has been examined using EBSD. Starting with a random texture in the cast condition, the material developed a ...typical β-fibre texture during the early stages of plane strain compression at a temperature of 375 °C. At strains higher than about 2, the “brass” texture component, {0
1
1}
〈2
1
1〉
, began to dominate the texture. The development of such a texture has been observed previously in aluminium alloys, particularly when fine particles effecting Zener pinning of grain boundaries are present. In the present case, measurements indicate that grain boundary migration during deformation was responsible for the development of the strong “brass” texture.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An analysis of the growth and stability of cellular microstructures, which takes account of the orientation dependence of boundary energies and mobilities, is presented and used to develop a simple ...unified theory of continuous and discontinuous recovery, recrystallization and grain growth. The analysis shows that low angle subgrain structures are intrinsically very unstable whilst medium to high angle structures may be very stable. The model is used to analyse discontinuous subgrain growth, primary recrystallization, the effects of texture on grain growth and the stability of highly strained metals.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
MUTYH-associated polyposis (MAP) is a recessive trait characterised by multiple colorectal adenomas and a high risk of colorectal cancer. MUTYH functions in the DNA base excision repair pathway and ...has a key role in the repair of oxidative DNA damage.
To assess the contribution of inherited variants in genes involved in base excision repair and oxidative DNA damage including MUTYH, OGG1, NEIL1, NEIL2, NEIL3, NUDT1 and NTH1 to the multiple colorectal adenoma phenotype.
Inherited variants of MUTYH, OGG1, NEIL1, NEIL2, NEIL3, NUDT1 and NTH1 were sought in 167 unrelated patients with multiple colorectal adenomas whose family histories were consistent with recessive inheritance. These variants were also characterised in approximately 300 population controls.
Thirty-three patients (20%) and no controls were MUTYH homozygotes or compound heterozygotes (ie, carried two mutations) and therefore had MAP. Eight different pathogenic MUTYH mutations were identified, of which four were novel. MAP cases had significantly more adenomas than non-MAP cases (p = 0.0009; exact test for trends in proportions) and presented earlier (p = 0.013; analysis of variance). Twenty-four protein-altering variants were identified upon screening of OGG1, NEIL1, NEIL2, NEIL3, NUDT1 and NTH1. However, all combinations of two (or more) variants that were identified at an individual locus in patients were also seen in controls, and no variants were significantly over-represented (or under-represented) in cases.
Multiple rare alleles of MUTYH are associated with autosomal recessive MAP, while OGG1, NEIL1, NEIL2, NEIL3, NUDT1 and NTH1 do not contribute significantly to autosomal recessive polyposis.
Diffusion bonding (DB) of superplastic 7075 Al alloy has been investigated for various temperatures, pressures and times, using a Gleeble 1500 test machine. After the removal of surface oxide, an ...organic solution was used to protect the surfaces prior to bonding. The strengths achieved after bonding were dependent on interface grain boundary migration and on grain growth during the bonding process. Under optimum conditions, bonds having parent metal shear strength and microstructure were obtained. The optimum temperatures for diffusion bonding, 510–520°C, corresponded with those at which the material exhibited optimum superplastic behavior. The characteristics and mechanisms of bonding are discussed.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This work describes some techniques developed for focused ion beam (FIB) serial sectioning and electron backscatter diffraction (EBSD) mapping of partially and fully recrystallized metals. A ...DualBeam™ platform was used to sequentially mill submicron slices of a material by FIB with the crystallographic features of each newly created surface characterized by EBSD. Two promising milling procedures are described which involve: (i) the generation of a small (∼
10–50 μm) diameter whisker for subsequent serial sectioning perpendicular to its long axis, and (ii) more extensive FIB milling of a larger sample to generate a protruding rectangular-shaped volume at the free surface. The latter was found to be the more powerful method of serial sectioning as the initial preparation is slightly less tedious. Using both techniques, serial sectioning was carried out on both recrystallized iron and partly recrystallized nickel samples. The serial sectioning technique revealed a number of features of the recrystallizing grains in nickel that are not clearly evident in 2-D EBSD micrographs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Copper single crystals of {110}(001) orientation were cold rolled and annealed at 300 deg C to study both the deformed state and early stages of static recovery. A homogeneous cellular substructure ...was generated during rolling with normal direction/rolling direction (ND-RD) sections revealing intersecting bands aligned at an acute angle to RD. These bands exhibit cyclic orientation changes about ND with amplitudes and wavelengths up to 10 deg and 10 mum, respectively. During annealing, cells situated at the extreme of these orientation perturbations undergo the most rapid coarsening; such a process is similar to the abnormal subgrain growth previously observed in {110}(001) oriented aluminium single crystals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Characterization of microstructures containing small grains or low‐angle grain boundaries by electron backscattered diffraction (EBSD) is limited by the spatial and angular resolution limits of the ...technique. It was found that the best effective spatial resolution (60 nm) for aluminium alloys in a tungsten‐filament scanning electron microscope (SEM) was obtained for an intermediate probe current which provided a compromise between pattern quality and specimen interaction volume. The same specimens and EBSD equipment when used with a field‐emission gun SEM showed an improvement in spatial resolution by a factor of 2–3. For characterizing low‐angle boundary microstructures, the precision of determining relative orientations is a limiting factor. It was found that the orientation noise was directly related to the probe current and this was interpreted in terms of the effect of probe current on the quality of the diffraction patterns.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
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