• T R Anantharaman

      Articles written in Proceedings – Section A

    • Electron-metallographic studies of precipitation in an aluminium-zinc-magnesium alloy

      J Ramesam M Ramakrishna Rao T R Anantharaman

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      The mechanism of sub-microscopic precipitation in an Al-Zn-Mg alloy selected for its maximum response to ageing has been studied by a standardized oxide-replica technique in a 100 kV. Philips Electron Microscope. Contrary to earlier conclusions, examination of the oxide replicas has been shown to reveal details of the precipitation process almost as clearly as the thin-foil transmission technique. The reported formation of spherical Guinier-Preston zones followed by the development of a Widmanstaetten pattern of precipitated platelets has been confirmed. The zones have, however, been shown to grow into the platelets andnot to dissolve in the matrix as reported earlier. The precipitation process has been correlated with the Hardness/Ageing Time curve and the structure of the precipitates has also been discussed.

    • X-ray line-breadth analysis of growth and deformation faulting in hexagonal close-packed structures

      P Rama Rao T R Anantharaman

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      Approximations employed so far in the evaluation of growth and deformation faulting in h.c.p. structures from integral and half-peak X-ray line breadths have been critically examined. An improved and yet simple procedure has been suggested to study faulting, mixed or otherwise, in h.c.p. structures. Necessary corrections for limitations of the measuring range have been worked out for integral and half-peak breadths over a wide range of growth and deformation fault parameters. The suggested procedure is illustrated by application to a study of faulting in spontaneously transformed cobalt powder.

    • Impact of thermal and mechanical treatment on faulting in hexagonal cobalt

      P Rama Rao T R Anantharaman

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      New results on the impact of thermal and mechanical treatment of pure cobalt on the content of the hexagonal phase and densities of growth as well as deformation stacking faults have been presented. The significance of these results along with those obtained by earlier investigators has been discussedvis-a-vis the spontaneous as also stress-induced f.c.c.→h.c.p. trans-formation in cobalt.

    • The constitution and structure of manganese-gallium alloys

      H G Meissner K Schubert T R Anantharaman

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      The constitution of manganese-gallium alloys has been investigated, chiefly by thermal analysis and X-ray methods. The binary phase diagram has been established, displaying eight peritectic, three eutectoidal and two peritectoidal reactions. Ten intermediate phases have been recognized and the structures of six of them have been resolved. The details of the constitutional diagram have been discussed in relation to allied systems and in the light of the valency electron interactions.

    • Influence of crystallite shape on particle size broadening of Debye-Scherrer reflections

      Shrikant Lele T R Anantharaman

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      Formulae for the Scherrer constant Kβ, the variance Scherrer constant Kω and the taper parameter Lω for crystals having the external shapes of a triangular prism, a square prism, a hexagonal prism and a cylinder have been obtained in terms of the reflection indices and proportionality factors,viz., the ratio of the height of the crystal to the square root of its basal area and the ratio of the two lattice constants of the unit cell. The numerical values of Kβ, Kω and Lω have also been computed for direct application in particular cases.

    • Electron-microscopic examination of a splat-cooled silver-germanium alloy

      P Furrer H Warlimont T R Anantharaman

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      Extremely rapid solidification of a Ag-15 at.% Ge alloy results in the formation of a highly irregular structure. The individual grains consist of a lamellar mixture of close-packed structures with different stacking sequences (f.c.c. and h.c.p. phases as well as long-period stacking structures), superposed with a high density of randomly arranged stacking faults. It is concluded that the structure observed at room temperature may have formed by martensitic transformation of a metastable b.c.c. phase which is formed first upon solidification.

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