• Gouthama

      Articles written in Bulletin of Materials Science

    • Electron microscopic studies on the effect of Sn addition on the ageing characteristics of Al-0.7% Mg2Si alloy

      Gouthama Kishore

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      The effect of trace addition of Sn on the ageing characteristics of Al-0.7% Mg2Si has been studied by hardness measurements and transmission electron microscopy. The changes observed in the microstructural features have been explained on the basis of the strong interaction existing between Sn atoms and quenched-in vacancies. At ageing temperatures below 200°C Sn addition brings about a ratardation in the kinetics of G.P. zone growth whereas at higher ageing temperatures, it aided the precipitate nucleation and growth. The hardness data agree well with the deductions based on observations made on the thin foils.

    • Alloy design of ductile phosphoric iron: Ideas from archaeometallurgy

      Gouthama R Balasubramaniam

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      Alloy design criteria to produce ductile phosphoric irons have been proposed based on a detailed microstructural study of ancient Indian irons. The alloy design aims at avoiding phosphorus segregation to the grain boundaries by

      soaking the phosphoric iron at high temperatures within the ferrite + austenite region to precipitate austenite allotriomorphs,

      utilizing a critical amount of carbon to segregate to grain boundaries, and

      precipitation of some of the phosphorus in solid solution in the ferrite matrix as fine coherent phosphide precipitates.

    • Porous copper template from partially spark plasma-sintered Cu–Zn aggregate via dezincification

      M Mandal D Singh Gouthama B S Murty S Sangal K Mondal

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      Present work deals with the preparation of spark plasma-sintered Cu–Zn aggregate (5, 10 and 20 wt% Zn) with interfacial bonding only starting from elemental powders of Cu and Zn (99.9% purity) and subsequently making of porous template of Cu by dezincification. Sintering is done so as to achieve only interfacial bonding with the aim to maintain maximum potential difference between the Cu and Zn particles during dezincification process in various solutions, viz. 1 N HCl and 3.5 wt% NaCl solutions. X-ray diffraction, optical microscopy and SEM–EDS are carried out to examine microstructural evolution and subsequent changes in hardness with sintering temperatures and different Zn percentages. Dezincification and pore formation are conducted on sintered 0.5 mm thick 12 mm diameter disc samples. The size, distribution and nature of pores in porous templates of Cu are then investigated using optical microscopy and SEM–EDS analysis.

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