• Vakil Singh

      Articles written in Bulletin of Materials Science

    • Effect of H+ ion irradiation on surface morphology of Fe40Ni40B20 metallic glass

      A J K Prasad Vakil Singh

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      The effect of irradiation by H+ ions on surface modifications of metallic glass Fe40Ni40B20, in the as-quenched, structurally related and crystallized state, has been studied. Swollen regions develop on the surface of the as-quenched and structurally relaxed specimens, whereas blisters form on the surface of the crystallized specimen, under identical conditions of irradiation. The results are explained in terms of the distribution of hydrogen in the amorphous and crystallized conditions.

    • Undercooling studies on dispersed bismuth droplets

      Sanjay Chaubey Vakil Singh P Ramachandrarao

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      In the zinc-bismuth system, a monotectic reaction occurs at 689 K and 0·6 at.% Bi composition. Rapid solidification of the as-cast monotectic alloy led to a micromorphology in which bismuth was uniformly and bimodally distributed as small droplets in the zinc matrix. Statistical analysis of the electron micrographs obtained from different transparent regions of the foils revealed that the size of most of the droplets was about 6 nm. These droplets undercooled by 132 K. An analysis of the nucleation rate measurements shows that the activation energy barrier to nucleation is of the order of 39·8 kcal/mol at the maximum undercooling.

    • Oxidation behaviour of the near α-titanium alloy IMI 834

      K V Sai Srinadh Vakil Singh

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      Oxidation behaviour of the near 𝛼-titanium alloy IMI 834 was investigated over a range of temperatures, from 600–800°C, in air. Specimens were solution-treated in the 𝛼 + 𝛽 and 𝛽 phase fields for 1 h and 1/2 h, respectively and cooled in air to room temperature. The solution treated samples were subjected to stabilization treatment at 700°C for 2 h, followed by cooling in air. Oxidation behaviour of these samples was studied from 600–800°C in air, for 50 h. The morphology of the scales formed was examined by SEM and the phases present in the scales were characterized by X-ray diffraction. While there was little oxidation at 600°C, the rate of oxidation increased at higher temperatures. In general, the rate of oxidation was found to be more in the 𝛼 + 𝛽 treated condition than that in the 𝛽 treated one. The results are discussed in terms of the characteristics of the oxide film formed under different conditions.

    • Effect of heat treatment on tensile behaviour of Ti–6Al–5Zr–0.5Mo–0.25Si alloy

      Anil Kumar Nag K V U Praveen Vakil Singh

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      Tensile behaviour of the near 𝛼 titanium alloy, Ti–6Al–5Zr–0.5Mo–0.25Si (LT26A), was investigated in (𝛼+𝛽) as well as 𝛽 treated condition, over a wide range of temperature from RT to 823 K. It was observed that there were distinct serrations on the load-elongation curves of the 𝛼 + 𝛽 treated material at intermediate temperatures from 623 to 723 K. Tensile tests at 673 K over a wide range of strain rate from 0.052 to 5.60 (× 10-2) s-1 showed negative strain rate sensitivity. Thus, occurrence of DSA was confirmed. It was established from the measured activation energy for DSA that it was essentially controlled by diffusion of the solid solution strengthener silicon in the matrix.

    • Low cycle fatigue behaviour of Ti–6Al–5Zr–0.5Mo–0.25Si alloy at room temperature

      Anil Kumar Nag K V U Praveen Vakil Singh

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      Low cycle fatigue (LCF) behaviour of the near 𝛼 titanium alloy, Ti–6Al–5Zr–0.5Mo–0.25Si (LT26A), was investigated in the (𝛼 + 𝛽) as well as 𝛽 treated conditions at room temperature. LCF tests were carried out under total strain controlled mode in the range of 𝛥 𝜀t/2: from ± 0.60% to ± 1.40%. The alloy shows cyclic softening in both the conditions. Also it exhibits dual slope Coffin–Manson (C–M) relationship in both the treated conditions.

    • Effect of anodization on corrosion behaviour and biocompatibility of Cp-titanium in simulated body fluid

      Archana Singh B P Singh Mohan R Wani Dinesh Kumar J K Singh Vakil Singh

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      The objective of this investigation is to study the effectiveness of anodized surface of commercial purity titanium (Cp-Ti) on its corrosion behaviour in simulated body fluid (SBF) and proliferation of osteoblast cells on it, to assess its potentiality as a process of surface modification in enhancing corrosion resistance and osseointegration of dental implants. Highly ordered nano-porous oxide layer, with nano-sized pores, is developed on the surface of Cp-Ti through electrochemical anodization in the electrolyte of aqueous solution of 0.5% HF at 15 V for 30 min at 24 °C. The nano-porous feature of the anodized surface is characterized by field-emission scanning electron microscope (FESEM). Pores of some anodized samples are sealed by exposing the anodized surface in boiling water. Corrosion behaviour of the anodized specimen is studied in Ringer’s solution at 30 ± 2 °C, using electrochemical impedance and cyclic polarization technique. Biocompatibility of the anodized surface is accessed using MG63 osteoblast cells. Both corrosion as well as pitting resistance of Cp-Ti in simulated body fluid are found to be highest in the anodized and sealed condition and followed in decreasing order by those of anodized and unanodized ones. Significantly higher MG63 osteoblast cell proliferations are found on the anodized surface than that on the unanodized one. Anodized Cp-Ti develops nano-size surface pores, like that of natural bone. It enhances corrosion and pitting resistance and also the process of osteoblast cell proliferation on Cp-Ti.

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