• M Ramakrishna Rao

      Articles written in Proceedings – Section A

    • Mineralogy of some Indian clays

      M Ramakrishna Rao

      More Details Abstract Fulltext PDF

      Mineralogical compositions of five Indian clays have been determined by the petrographic, X-ray, electron-microscopic and differential thermal analysis methods. The relative importance of the methods is discussed and the procedures are described.

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

      J Ramesam M Ramakrishna Rao T R Anantharaman

      More Details Abstract Fulltext PDF

      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.

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