• P Rama

      Articles written in Bulletin of Materials Science

    • Foreword

      P Rama K J Rao S K Joshi C N R Rao S V Subramanyam

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    • Foreword

      P Rama Rao

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    • Foreword

      P Rama Rao K J Raj

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    • Foreword

      P Rama Rao K J Rao D Chakravorty H S Maiti

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    • Editorial

      K J Rao P Rama

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    • Effect of alloying additions onKISCC of ultrahigh strength NiSiCr steel

      S V Kamat G Malakondaiah M Srinivas J Marthanda Murthy P Rama Rao

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      The effect of alloying additions viz. cobalt, molybdenum, cerium and a combination of cobalt and molybdenum, on theKISCC of NiSiCr steel in 3·5% NaCl aqueous solution was studied. Addition of cobalt to NiSiCr steel resulted in an increase in theKISCC whereas molybdenum addition decreased theKISCC. Cerium addition did not affect theKISCC while the combination of cobalt and molybdenum resulted in an increase in theKISCC although not as much as in the case of cobalt addition. The effect of alloying elements onKISCC could be attributed to their effect on the critical fracture stress and yield strength.

    • Basic studies leading to the development of an ultrahigh strength, high fracture toughness low-alloy steel

      G Malakondaiah M Srinivas P Rama Rao

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      Ultrahigh strength steels have been used increasingly in recent years for critical aircraft and aerospace structural applications. In such applications, though materials performance is of prime consideration, cost and availability makes the low-alloy steels an attractive option. This paper describes the development of an ultrahigh strength NiSiCrCoMo low-alloy steel, supported by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture resistance of iron, with and without the presence of carbon. The results of the basic studies, in combination with the work of Garrison (1986) on a NiSiCr steel, have profitably been employed in the development of a NiSiCrCoMo low-alloy steel possessing a strength-toughness combination quite comparable to the highly alloyed 250-grade maraging steel. Reproducibility of attractive strength and toughness properties has been established in tonnage scale melts. This steel, in the softened condition, has good formability and machinability. Weld parameters have also been established. The NiSiCrCoMo low-alloy steel thus meets the requirements of performance and cost rendering it an attractive option for advanced structural applications.

    • Crystallization and kinetics studies of Ti$_{20}$Zr$_{20}$Cu$_{60−x}$Ni$_x$ ($x = 10$, 20, 30 and 40) metallic glasses

      P RAMA RAO ANIL K BHATNAGAR BHASKAR MAJUMDAR

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      Synthesis and characterization of Ti$_{20}$Zr$_{20}Cu$_{60−x}$ Ni$_x$ ($x = 10$, 20, 30 and 40) metallic glasses are reported in this paper. Glassy ribbons are produced by rapid quenching using the standard copper wheel roller technique in argon atmosphere. Their structural characterization is carried out by X-ray diffraction (XRD) and thermal behaviour (crystallization) study by differential scanning calorimetry (DSC). Results of XRD on both sides of each ribbon sample confirmed that each sample was indeed amorphous/glassy as only a very broad peak in XRD pattern was observed. Metallic glass Ti$_{20}$Zr$_{20}$Cu$_{50}$Ni$_{10}$ shows three crystallization peaks in non-isothermal DSC scans while other three samples show only a single crystallization peak. The activation energy of crystallization for each sample has been calculated using three available models, namely, those of Kissinger, Augis–Bennett and Ozawa. All the three models gave nearly similar activation energies for a given sample within 10%.

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