• V Singh

      Articles written in Bulletin of Materials Science

    • Role of Ti3Al/silicides on tensile properties of Timetal 834 at various temperatures

      K V Sai Srinadh Nidhi Singh V Singh

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      Extremely fine coherent precipitates of ordered Ti3Al and relatively coarse incoherent precipitates of 𝑆2 silicide exist together in the near 𝛼-titanium alloy, Timetal 834, in the dual phase matrix of primary 𝛼 and transformed 𝛽. In order to assess the role of these precipitates, three heat treatments viz. WQ, WQ–A and WQ–OA, were given to have no precipitates, Ti3Al and silicide and only silicide precipitates in the respective conditions. Tensile properties in the above three heat treated conditions were determined at room temperature, 673 K and 873 K. It was observed that largely Ti3Al precipitates were responsible for increase in the yield strength and decrease in ductility in this alloy.

    • Blistering in alloy Ti–6Al–4V from H+ ion implantation

      B K Singh V Singh

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      The effect of H+ ion implantation on surface morphology of the titanium alloy, Ti–6Al–4V, was studied, following H+ ion implantation of 150 keV and 250 keV energy to fluence of 2.6 × 1018 cm-2 and 2.5 × 1019 cm-2, respectively at ambient temperature. No detectable change was observed in surface features of either of the above specimen immediately after the implantation. However, vein like features (VLF) were observed to appear on the surface of the sample, implanted at 150 keV to a fluence of 2.6 × 1018 cm-2, following natural ageing at room temperature for 150 days. Subsequent annealing of the above naturally aged sample, at 423 K for 150 min under vacuum (10-3 torr), led to development of a macroblister.

      In sharp contrast in the other sample, implanted by H+ ions of higher energy (250 keV) to higher fluence of 2.5 × 1019 cm-2, neither there was any effect of natural ageing following the implantation nor that of subsequent annealing at 423 K and ageing on its surface morphology.

    • Structure and electric transport properties of LnSr2FeTiO7 (Ln = La, Nd and Gd)

      Suresh Gupta V Singh B L Sharma Indu Bhushan Sharma

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      Three new phases with compositions, LaSr2FeTiO7, NdSr2FeTiO7 and GdSr2FeTiO7, were prepared by the traditional ceramic method. Lazy–Pulverix analysis of the X-ray diffraction data suggests that the phases crystallize in the RP-type (𝑛 = 2) structure in the space group, 𝐼4/𝑚𝑚𝑚. The cell dimensions along the 𝑐-axis decrease with decrease in size of the rare earth ions. Electrical resistivity, as a function of temperature, shows that the materials are insulators and the resistivity decreases with decrease in the size of the rare earth ion, which is attributed to increase in the three-dimensional character.

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