Browsing by Author "T.R. Anantharaman"
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PublicationLetter A comment on "a decade of quenching from the melt" by T. R. Anantharaman and C. Suryanarayana (J. Mater. Sci 6 (1971) 1111-1135)(Kluwer Academic Publishers, 1972) H. Jones; T.R. Anantharaman; C. Suryanarayana[No abstract available]PublicationArticle A modified technique for preparing disk specimens for transmission electron microscopy(1968) R.P. Wahi; D.L. Bhattacharya; T.R. AnantharamanThis note describes a modified 'holder technique' for preparing thin metal foils for transmission electron microscopy. In this, profiling of the sample and determination of the exact moment of perforation are carried out relatively more easily than in the earlier techniques.PublicationArticle An electron-microscopic investigation of the transformation behaviour of Al6Mg4Cu quasi-crystalline alloy(1988) V.Venkateswara Rao; T.R. AnantharamanIn the melt-spun icosahedral Al6Mg4Cu alloy, non-uniform grain size distribution and overlapping grains giving rise to periodic Moire patterns were noted. On heating, this phase was observed to transform through the formation of nuclei, predominantly at the grain boundaries, but occasionally also inside the grains. In the early stages, some semicoherent phase appeared to form but transformed eventually to the equilibrium phase, with the formation of holes. Lattice imaging of the partially transformed alloy revealed both the icosahedral and transforming phases to be periodic. The present observations on structure and transformation behaviour seem to be consistent with a model based on pentagonal chains present in the liquid and as-quenched alloys. © 1988.PublicationArticle An improved piston-and-Anvil technique for quenching liquid metals(1970) P. Ramachandrarao; D. Banerjee; T.R. Anantharaman[No abstract available]PublicationArticle Atomic arrangements in Al‒Mn and Al‒Li‒Cu icosahedral crystals(1988) T.R. Anantharaman[No abstract available]PublicationArticle CHALLENGES OF THE AMORPHOUS STATE.(1986) T.R. AnantharamanAmorphous materials of different types and properties are today produced by diverse techniques like slow or rapid cooling from the liquid state, vapour deposition, sputtering, electrodeposition, solid-state diffusion and even ion bombardment. Amorphous solids can display different types of properties and may be non-conducting, semiconducting, metallic, superconducting etc. , depending on their chemical constituents and composition. It has become abundantly clear that amorphous materials in general and glasses in particular exhibit the same range of electronic behavior as crystalline materials, and the theory of solids is slowly getting modified to recognize this fact. The author briefly review metallic glasses, quasicrystals, and semiconducting glasses.PublicationArticle Comments on the proposed formation of stacking faults in an AlZn alloy during high-temperature ageing(1971) R.P. Wahi; P.Rama Rao; T.R. Anantharaman[No abstract available]PublicationArticle Decomposition studies of a liquisol quenched Al-33 at.% Mg alloy(1979) S.K. Tiwari; K. Chattopadhyay; C. Suryanarayana; T.R. AnantharamanX-ray and electron metallographic studies were undertaken on an aluminum-33 at.% magnesium alloy rapidly quenched from the melt by the "gun" technique. A small supersaturation of Mg in Al and two metastable intermediate phases were detected. These phases were found to display complex decomposition behavior on annealing at temperatures up to 300°C. © 1979.PublicationLetter Deformation faulting in titanium, zirconium and hafnium(1967) Shrikant Lele; T.R. AnantharamanAn x-ray study of deformed Ti, Zr and Hf was performed. A Fourier analysis of line profiles revealed an absence of faulting in Zr and Hf while a small deformation fault probability (0·008) was found for deformed Ti. The results are discussed in the light of earlier results and present theories on deformation faulting. © 1967, Taylor & Francis Group, LLC.PublicationArticle Electron-microscopic evidence for heavy faulting in silver-germanium alloys on rapid solidification(1970) P. Furrer; T.R. Anantharaman; H. WarlimontSilver-germanium alloys of five different compositions in the range 5-22 at. % Ge were quenched from the melt by the gun technique and immediately subjected to transmission electron-microscopic examination. The observations confirm earlier x-ray evidence for light to heavy random faulting in both f.c.c. and h.c.p. phases on solidification. There is also evidence for formation of close-packed structures with regular long-period stacking sequences (up to 24 layers) and random stacking faults in alloys containing 10-22 at. % Ge. The quenched foils are found to have a generally random orientation of grains, even in sections having extremely fine grains (less than 500 A). © 1970 Taylor & Francis Group, LLC.PublicationArticle Formation of faulted close-packed structures in silver-germanium alloys quenched from the Melt(1969) P. Ramachandrarao; T.R. AnantharamanA series of silver—germanium alloys containing up to 25 at. % Ge was rapidly cooled from the liquid state by the Duwez technique and subjected to x-ray examination. The Debye-Scherrer patterns of the liquid-quenched alloys provide the first experimental proof for the incidence of light to heavy faulting in f.c.c. and h.c.p. phases on solidification. © 1969 Taylor & Francis Group, LLC.PublicationConference Paper HIGH-STRENGTH ALUMINIUM ALLOYS THROUGH RAPID SOLIDIFICATION PROCESSING.(Trans Tech Publ, 1985) C. Suryanarayana; P. Ramachandrarao; T.R. AnantharamanThe techniques of rapid solidification are over two decades old and their beneficial effects, viz. , refinement of grain size, extension of solid solubility limits and formation of metastable intermediate phases as well as metallic glasses are now well established. After reviewing the various principles and techniques available to quench or rapidly solidify metallic melts at very high cooling rates, methods of consolidating the rapidly-solidified particulates are described. The types of microstructures developed and their control are discussed. A critical review of the literature reveals that the above-mentioned metastable effects of rapid solidification either singly or jointly lead to improved properties of the materials. New alloys can now be designed from first principles to achieve high specific strength and high specific modulus of elasticity. The development work done in aluminium alloys is reviewed with special reference to the Varanasi investigations.PublicationArticle Icosahedral al6-mg4-cu: Interpretation of x-ray reflections and electron micrographs(1989) V.V. Rao; T.R. AnantharamanConventional and synchrotron X-ray diffraction patterns from i-Al6Mg4Cu have been indexed on the basis of a tetragonal unit cell. Periodic Moire and lattice fringes observed in TEM support the new structural model. © 1989, Taylor & Francis Group, LLC. All rights reserved.PublicationArticle Impact of substrate temperature on rapid solidification of an Al-Cu eutectic alloy(Kluwer Academic Publishers, 1982) R.K. Singh; K. Chattopadhyay; S. Lele; T.R. AnantharamanAn aluminium-copper eutectic alloy has been subjected to rapid solidification, utilising the "gun" technique, with different substrate temperatures to evaluate its influence on the cooling rate and microstructure. At all temperatures, the microstructure is essentially non-uniform and consists of metastable solid solution (with decomposition products) as well as eutectic regions. The solid state decomposition of the metastable solid solution is strongly dependent on the substrate temperature and leads to the formation of different metastable precipitates and consequent changes in microstructure. The origin of the different microstructures is discussed. © 1982 Chapman and Hall Ltd.PublicationArticle Impact of thermal and mechanical treatment on faulting in hexagonal cobalt(1965) P. Rama Rao; T.R. AnantharamanNew 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 discussed vis-a-vis the spontaneous as also stress-induced f.c.c.→h.c.p. trans-formation in cobalt. © 1965 Indian Academy of Sciences.PublicationArticle Imperfections in Copper‐Silicon Filings(1965) P. Rama Rao; T.R. AnantharamanDetailed X‐ray line‐broadening studies are made on deformed filings of Cu96Si4, Cu92Si8, Cu90Si10, and Cu89Si11 alloys. The f.c.c. deformation fault parameters in fresh filings of the first three alloys, in each case of two different grain sizes, are determined by the Paterson method. Stacking‐fault contributions to the observed diffraction broadening are eliminated by a procedure suggested by Christian and Spreadborough, and the domain size and lattice strain effects are separated by single line Fourier analysis. The fresh filings of the two‐phase Cu89Si11 alloy show only the faulted h.c.p. structure, the f.c.c. phase having disappeared during deformation by filing. The fault parameter, domain size, and lattice strain values in the strain‐induced h.c.p. phase are also estimated. Copyright © 1965 WILEY‐VCH Verlag GmbH & Co. KGaA, WeinheimPublicationArticle Influence of copper on tempering a low-carbon chromium steel with and without small Nb or Ti additions(1974) K.B. Mishra; D.S. Sarma; T.R. AnantharamanThe influence of 2% Cu on the tempering behavior of a low-carbon 4% Cr steel has been studied with and without small additions of Nb (0.09%) or Ti (0.21%) using hardness, optical and electron-microscopic techniques. Copper contributes significantly to precipitation hardening of Cr steel between 400 and 500°C. Addition of Nb or Ti enhances this hardening effect, which is established as essentially due to precipitation in the lath martensite of uniformly distributed spherical particles, presumably of copper. © 1974.PublicationArticle Influence of crystallite shape on particle size broadening of Debye-Scherrer reflections(1966) Shrikant Lele; T.R. AnantharamanFormulae 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. © 1966 Indian Academy of Sciences.PublicationArticle Metallography of rapidly solidified aluminum-germanium alloys(1971) C. Suryanarayana; T.R. Anantharaman[No abstract available]PublicationArticle Microstructure of melt-spun Al-24 at% Mn alloy(1988) V. Venkateswara Rao; T.R. Anantharaman[No abstract available]