BHU Institutional Repository :: Browsing by Author "Chattopadhyay, K."

Browsing by Author "Chattopadhyay, K."

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Decomposition studies of a liquisol quenched Al-33 at.% Mg alloy
(1979) Tiwari, S.K.; Chattopadhyay, K.; Suryanarayana, C.; Anantharaman, T.R.
X-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.
Effect of build orientation on wear and erosion behavior of maraging steel processed by powder bed fusion using laser beam (PBF-LB)
(Institute of Physics, 2022) Vishwakarma, Jaydeep; Chattopadhyay, K.; Srinivas, N C Santhi
The wear and erosion behavior of additively manufactured maraging steel with built orientations of 0°, 45° and 90° were investigated and compared with conventional (cast and hot rolled) samples. To investigate the effect of heat treatment, processed samples were subjected to solution treatment and ageing. As-built (AB) and heat-treated (HT) samples were wear-tested at various loads of 20N, 40N and 80N, at constant disc speed and specific sliding distance. Erosion tests were performed at 90° impingement angle for 40 min with erosion discharge rate of 4.5 g min-1, wear rate was found increasing with the increase in load from 20N to 80 N, and was found affected by build orientation, mainly in the as-built additive samples. In both, as built as well heat-treated conditions, 90° oriented samples were found more wear-resistant. However, wear resistance of the heat-treated samples was observed to be relatively higher as compared to that of as-built samples. Coefficient of friction (COF) decreased with increase in load, in both as built as well heat-treated conditions. Erosion resistance of the as-built (AB) and heat-treated (HT) samples in 0° orientation was higher than that of other build orientations. Prior to heat treatment, erosion resistance of the conventional samples was inferior to that of additive samples, due to comparatively coarser microstructure; however, after the heat treatment, erosion resistance was increased. Worn and eroded samples were examined under SEM and AFM. At low load of 20 N, abrasive wear by ploughing and at high load of 80N, adhesive wear was noticed. Erosion occurred mainly by lip formation and plastic deformation. © 2022 IOP Publishing Ltd.
Effect of LASER shock peening on microstructure, mechanical properties and corrosion behavior of interstitial free steel
(Elsevier B.V., 2015) Shadangi, Y.; Chattopadhyay, K.; Rai, S.B.; Singh, V.
LASER shock peening (LSP) is an effective process of surface modification. This work is concerned with the effect of LSP on the modification of microstructure, hardness, microhardness profile, residual stress, tensile properties and corrosion behavior of interstitial free (IF) steel. In order to study the effect of pulse energy on hardness, samples were subjected to LSP at pulse energy of 170, 230, 290 and 340. mJ respectively. The effect of LSP time on hardness, microhardness profile and tensile properties was investigated by processing the samples for 5, 10, 15 and 20. min at pulse energy of 230. mJ and there was found to be significant increase in tensile strength. There was grain refinement to nano level in the surface region due to LSP. Hardness was observed to increase by LSP up to 10. min and tensile strength increased up to LSP of 5. min. However with the increase in LSP time beyond 10. min there was prominent ablation and melting. The effect of overlapped (OV) LASER shocks was also studied by comparing their behavior with that of single shock. The potentiodynamic polarization study showed significant increase in corrosion resistance of the LSPed IF steel. © 2015 Elsevier B.V.
Effect of Surface Nanostructuring on Gene Expression for Protein Synthesis, Osteoblast Cells Recruitment and Size of Focal Adhesion: A Review
(Apple Academic Press, 2022) Raj, Nancy; Agrawal, Rahul; Chattopadhyay, K.; Bansal, R.; Singh, V.
Dental implants provide oral rehabilitation by mimicking bone topography, faster bone formation, and rapid bone healing to enable early loading protocol with better stability. The dental implant surface affects the mechanical stability of the implant affecting cell adhesion and osteogenic cell response. Different techniques have shown biological advantages through increase in surface wettability, surface roughness, and altered surface topography. These have benefitted osseointegration in both healthy as well as a compromised bone through its underlying cellular mechanisms. The effects of nanostructuring are discussed in this chapter in terms of gene expression, biochemical stimuli, biocompatibility, corrosion resistance, cell metabolism, and its differentiation. © 2022 Apple Academic Press, Inc.
Impact of substrate temperature on rapid solidification of an Al-Cu eutectic alloy
(Kluwer Academic Publishers, 1982) Singh, R.K.; Chattopadhyay, K.; Lele, S.; Anantharaman, T.R.
An 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.
Influence of build orientation and aging on corrosion behaviour of 18Ni300 maraging steel produced via Powder Bed Fusion using Laser Beam (PBF-LB)
(Elsevier Ltd, 2023) Vishwakarma, Jaydeep; Chattopadhyay, K.; Srinivas, N.C. Santhi
Conventional maraging steel corrodes uniformly but additive manufactured (AM) maraging steel can corrode differently, depending upon the angle of exposure of build layers to the corrosive media. The primary objective of this investigation is to examine the effect of build orientation and solution aging treatment (HT) on the corrosion behaviour of the AM maraging steel and to compare with that produced through the conventional route of casting and hot rolling. In this investigation, corrosion behaviour of maraging steel samples produced by Powder Bed Fusion using Laser Beam (PBF-LB), with different build orientations of 0°, 45°, and 90°, was investigated in a 3.5% NaCl solution. Corrosion resistance of the as-built (AB) samples was found to increase with decrease in the angle of inclination and related to structural heterogeneity and grain boundary density. However, corrosion resistance of the AB samples was decreased following heat treatment (solutioning and aging) and was controlled by precipitation of intermetallic phases and reversed austenite generation. While there was dominance of protective oxide layer of TiO2 in the AB and conventional sample, this oxide layer was not observed on the heat treated (HT) samples. Further, a marked difference was observed in pitting corrosion of the AB and HT samples. © 2023 Elsevier Ltd
Metastable phase formation and decomposition in a rapidly solidified aluminium-platinum alloy
(1979) Chattopadhyay, K.; Ramachandrarao, P.
The metastable phase formation and decomposition behaviour of a rapidly solidified Al-2 at.% Pt alloy were studied by electron microscopy and X-ray diffraction techniques. Two metastable phase were detected. One of them has a cubic structure with a = 5.67 A ̊ and can be considered as a metastable extension of the equilibrium Al2Pt phase. The other phase, of composition Al6Pt, has an orthorhombic structure with lattice parameters a = 15.762 A ̊, b = 12.103 A ̊ and c = 8.318 A ̊ and is isostructural with the equilibrium phase Ga6Pt. In the as-splat foils, the Al2Pt phase forms at the interdendritic regions whereas Al6Pt forms at the predendritically solidified regions. After prolonged aging the Al6Pt phase grows with the dissolution of the Al2Pt phase. The mechanisms of formation of the Al6Pt phase during artificial aging and natural aging are different. While normal nucleation processes control the decomposition during artificial aging, sympathetic nucleation of Al6Pt is the dominant mode of decomposition in the naturally aged foils and leads to a star-like morphology. The reasons for the formation of the above metastable phases are also discussed. © 1979.
Microstructure and mechanical properties of Al-CuAl2 eutectic alloys solidified over a heat pipe
(Kluwer Academic Publishers, 1983) Ojha, S.N.; Chattopadhyay, K.; Ramachandrarao, P.
Microstructural studies and mechanical properties of Al-CuAl2 eutectic alloys solidified over a heat pipe have been presented and discussed. The role of thermal undercooling produced by solidification over a heat pipe in controlling the microstructure has been highlighted. Tensile specimens fabricated from aligned cellular Al-CuAl2 eutectic regions are shown to have maximum strength at intermediate temperatures of 450 to 500 K. Variations in the relative plasticity of two constituent phases of the eutectic are held responsible for the temperature dependence of strength. © 1983 Chapman and Hall Ltd.
Multiply twinned particles in an aluminium-nickel vapour deposit
(1976) Chattopadhyay, K.; Ramachandrarao, P.
Thin foils of a solid solution of nickel in aluminium, obtained by vapour deposition on air cleaved mica at room temperature, were studied by electron microscopy. Multiply twinned particles could be detected in these foils. © 1976.
On Al2M-type phases in splat cooled aluminium alloys
(Kluwer Academic Publishers, 1978) Chattopadhyay, K.; Lele, S.; Ramachandrarao, P.
[No abstract available]
On the occurrence of twinned dendrites in rapidly solidified aluminum alloys
(1980) Chattopadhyay, K.; Lele, S.; Ramachandrarao, P.
Evidence has been presented for the occurrence of twinned dendrites in rapidly solidified aluminum alloys containing nickel, platinum and zinc. Their existence offers an alternate explanation for the characteristic elongated parallel grain morphology in liquid quenched aluminum alloys. It is argued that twinned dendrites can be stabilised even at high growth rates by a non-equilibrium solute trapping. © 1980.
Phase transformations and metastable phase equilibria in AlGe alloy
(1985) Ojha, S.N.; Chattopadhyay, K.; Ramachandra Rao, P.
In this paper the results of a detailed investigation on the metastable phase relations in undercooled as well as rapidly solidified AlGe alloys containing 2-50 at.% Ge are reported. Data obtained on the structure and morphology of phases enable us to arrive at the phase relations and transformation processes occurring in undercooled and rapidly quenched melts of this system. These results are explained with the help of a metastable phase diagram consisting of a peritectic and eutectic reaction involving metastable phases. © 1985.
Rapid solidification and decomposition of a hypomonotectic Al-Cd alloy
(Kluwer Academic Publishers, 1980) Chattopadhyay, K.; Ramachandrarao, P.
Rapid solidification of Al-1.5at % Cd alloy can lead to a wide variety of morphologies. The sequence of the morphologies with increasing foil thickness is single phase → elongated cell → hexagonal cell → dendrite. Monotectic reaction ahead of the solid-liquid interface leads to a unique distribution of the cadmium particles. Models are proposed to explain the genesis of the distribution of these particles. The study of the decomposition behaviour confirms the existence of a preprecipitation stage. The G.P. zones are found to be spherical and lead to a precipitate-free zone near grain/cell boundaries. The coarsening of the precipitates at liquid temperatures takes place by the migration and coalescence of the droplets. © 1980 Chapman and Hall Ltd.
Revisiting Quasicrystals for the Synthesis of 2D Metals
(Springer, 2022) Yadav, Thakur Prasad; Kumbhakar, Partha; Mukhopadhyay, N.K.; Galvao, Douglas S.; Ajayan, P.M.; Ranganathan, S.; Chattopadhyay, K.; SekharTiwary, Chandra
Quasicrystals (QCs) are intermetallic materials with long-range ordering but with lack of periodicity. They have attracted much interest due to their interesting structural complexity, unusual physical properties, and varied potential applications. The last four decades of research have demonstrated the existence of different forms of QC composed of several metallic and non-metallic systems, which have already been exploited in several applications. Recently, with the experimental realization of 2D (atomically thin) metals, the potential applications of these structures have significantly increased (such as inflexible electronics, optoelectronics, electrocatalysis, strain sensors, nano-generators, innovative nano-electromechanical systems, and biomedical applications). As a result, high-quality 2D metals and alloys with engineered and tunable properties are in great demand. This review summarizes the recent advances in the synthesis of 2D single and few layered metals and alloys using quasicrystals. These structures present a large number of active sites for hydrogen evolution process catalysis and other functional properties. In this review, we also highlighted the possibility of using QC to synthesize other 2D metals and to explore their physical and chemical properties. © 2022, The Indian Institute of Metals - IIM.
SOLIDIFICATION OF UNDERCOOLED LIQUID ALLOYS ENTRAPPED IN SOLID - A STRUCTURAL INVESTIGATION.
(North-Holland, 1985) Prasad, Y.V.S.S.; Agarwal, S.L.; Chattopadhyay, K.; Ramachandrarao, P.
[No abstract available]
The nature of non-equilibrium solidification of undercooled AgCu alloys in contact with primary copper dendrites
(1984) Prasad, Y.V.S.S.; Ramachandra Rao, P.; Chattopadhyay, K.
Liquids of silver-copper alloys with near eutectic compositions embedded in a copper matrix were undercooled. The structural and microstructural investigations of these alloys solidified from undercooled temperature indicated the absence of both the eutectic reaction and diffusionless transformation below the equal free energy curve (T0). Instead the liquid maintained local equilibrium with the copper dendrites continuously until it intersected the extended solidus of the silver rich solid solution. © 1984.

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