• G K Dey

      Articles written in Pramana – Journal of Physics

    • Carbide precipitates in solution-quenched PH13-8 Mo stainless steel: A small-angle neutron scattering investigation

      D Sen A K Patra S Mazumder J Mittra G K Dey P K De

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      This paper deals with the small-angle neutron scattering (SANS) investigation on solution-quenched PH13-8 Mo stainless steel. From the nature of the variation of the functionality of the profiles for varying specimen thickness and also from the transmission electron microscopy (TEM), it has been established that the small-angle scattering signal predominantly originates from the block-like metallic carbide precipitates in the specimen. The contribution due to double Bragg reflection is not significant in the present case. The single scattering profile has been extracted from the experimental profiles corresponding to different values of specimen thickness. In order to avoid complexity and non-uniqueness of the multi-parameter minimization for randomly oriented polydisperse block-like precipitate model, the data have been analyzed assuming randomly oriented polydisperse cylindrical particle model with a locked aspect ratio.

    • On amorphization and nanocomposite formation in Al-Ni-Ti system by mechanical alloying

      N Das G K Dey B S Murty S K Pabi

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      Amorphous structure generated by mechanical alloying (MA) is often used as a precursor for generating nanocomposites through controlled devitrification. The amorphous forming composition range of ternary Al-Ni-Ti system was calculated using the extended Miedema’s semi-empirical model. Eleven compositions of this system showing a wide range of negative enthalpy of mixing (−ΔHmix) and amorphization (−ΔHamor) of the constituent elements were selected for synthesis by MA. The Al88Ni6Ti6 alloy with relatively small negative ΔHmix (−0.4 kJ/mol) and ΔHamor (−14.8 kJ/mol) became completely amorphous after 120 h of milling, which is possibly the first report of complete amorphization of an Al-based rare earth element free Al-TM-TM system (TM = transition metal) by MA. The alloys of other compositions selected had much more negative ΔHmix and Hamor; but they yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the as-milled condition, evidencing a high degree of stability of the intermetallic phases under the MA environment. Hence, the negative ΔHmix and ΔHamor are not so reliable for predicting the amorphization in the present system by MA

    • Solidification and microstructural aspects of laser-deposited Ni–Mo–Cr–Si alloy on stainless steel

      Reena Awasthi Santosh Kumar D Srivastava G K Dey

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      Laser cladding of stainless steel substrate was carried out using Ni–32Mo–15Cr–3Si (wt%) alloy powder. Laser cladding parameters were optimized to obtain defect-free and metallurgically bonded clad. Variation in solidification rate, cooling rate and compositional variation resulted in heterogeneous microstructure. Microstructure was found to be distinctly different in regions of clad cross-section. Majority of the region was found to consist of eutectic of Mo-rich hcp intermetallic Laves phase and NiFe fcc gamma solid solution phases. Extensive microstructural examinations of different clad regions have been carried out using microscopy and microanalysis techniques.

    • Laser pulse heating of nuclear fuels for simulation of reactor power transients

      C S Viswanadham K C Sahoo T R G Kutty K B Khan V P Jathar S Anantharaman Arun Kumar G K Dey

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      It is important to study the behaviour of nuclear fuels under transient heating conditions from the point of view of nuclear safety. To simulate the transient heating conditions occurring in the known reactor accidents like loss of coolant accident (LOCA) and reactivity initiated accident (RIA), a laser pulse heating system is under development at BARC, Mumbai. As a prelude to work on irradiated nuclear fuel specimens, pilot studies on unirradiated UO2 fuel specimens were carried out. A laser pulse was used to heat specimens of UO2 held inside a chamber with an optically transparent glass window. Later, these specimens were analysed by metallography and X-ray diffraction. This paper describes the results of these studies.

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