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Browsing Academic Staff by Keyword "alloys"

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    The influence of elastic strain on the shape of particles segregating in an alloy
    (Physical Society, 1940) Nabarro, F.R.N.
    An estimate is given of the way in which the strain energy associated with a particle of precipitate depends upon the shape of the particle. It is shown that the energy can only be reduced if the precipitate forms in flat plates, and then only in the case of particles which have broken away from the lattice of the matrix. this dependence of strain energy on shape causes the precipitate to consist of plates of a shape similar to that observed in Widmanstatten structures.
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    The mechanical properties of metallic solid solutions
    (Physical Society, 1946) Nabarro, F.R.N.
    The theoretical relation between the lattice strains produced by precipitation in a mineral and the corresponding increase in hardness is extended to the case of lattice strains in metallic solid solutions. The elastic limit of a single crystal of a solid solution is calculated on the assumption that the crystal will slip when the applied external stress is equal to the mean value of the internal stress. This mean is taken over the length of a dislocation, assumed to be in numbers 1000 atoms. The estimate agrees in order of magnitude with the experimental observations. Similar considerations are applied to the hardness of polycrystalline solid solutions. The theory is extended to cases in which the increase of hardness produced by alloying is not large in comparison with the hardness of the pure solvent.
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    The strains produced by precipitation in alloys
    (Royal Society of London, 1940) Nabarro, F.R.N.
    If the process in metals results simply in the interchange of pairs of atoms large strains must be set up when a new phase prcipitates in an alloy. The strain energy involved is calculated for particles of precipitate of various shapes, and is found to be least if the precipitate forms thin plates. The shape of the particle actually formed is influenced by this energy, by the degree of supersaturation of the solid solution, and by surface effects; the calculated shape is shown to agree reasonably well with that observed experimentally.