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Item Local stress and strain variations in the deformation zone can be ascertained by measuring hardness. Hardness is correlated with strain and stress. The expressions discussed later are useful in determining the local variations in stress and strain from hardness measurement. It is a simple method compared to visioplasticity. One can estimate the forces required for a forming process. It helps in the choice of equipment, design of tooling and selection of lubricant for the particular process.(Indian Academy of Sciences, Hardness-stress-strain correlation in aluminium - A simpler alternative to visioplasticity in metal forming) Dharmaveera, N.; Srinivasan, K.1996Item Heat transfer at the metal/chill interface during solidification of commercially pure aluminium square bar castings with cast iron chill at one end was investigated. Experiments were carried out for different chill thicknesses and superheats. The inner surface temperature of the chill initially was found to increase at a faster rate for higher superheats. The effect of chill thickness on the inner surface temperature of the chill was observed only after the heat from the solidifying casting had sufficient time to diffuse to the interior of the chill material. Inverse analysis of the non-linear one-dimensional Fourier heat conduction equation indicated the occurrence of peak heat flux at the end of filling of the mould. The effect of superheat on heat flux was minimal after filling. However, the effect of chill thickness had a significant effect on the heat flux after the occurrence of peak heat flux. Higher heat flux transients were estimated for castings poured at higher superheats. The corresponding heat transfer coefficients were also estimated and reported. The heat flux model presented in this work can be used for determination of casting/chill interfacial heat flux as a function of chill thickness and superheat. These heat flux transients could be used as boundary conditions during numerical simulation of solidification of the casting. © 2002 Elsevier Science B.V. All rights reserved.(Effect of chill thickness and superheat on casting/chill interfacial heat transfer during solidification of commercially pure aluminium) Gafur, M.A.; Haque, M.N.; Prabhu, K.2003Item SiC particulate reinforced A356 Al metal matrix composites were laser treated using pulsed Nd-YAG laser beam. The processing was carried out in air atmosphere at varying pulse energy (5 to 20 J) and scan rates (30 to 150 mm/sec). The samples were cut perpendicular to the track and they were characterized using optical microscopy, scanning electron microscopy and X-ray diffraction. Microstructure of laser treated region consists of regular succession of coarse and fine microstructure signifying the presence of low velocity bands. Transition from cellular/columnar dendritic to equiaxed dendritic structure has been observed. Microstructure of samples laser treated with specific energy greater than 13 kJ/cm2 show presence of Al 4C3 platelets. © 2004 Kluwer Academic Publishers.(Microstructural studies in low specific energy laser surface treated Al(A356)-SiCp composites) Bhat, K.U.; Surappa, M.K.2004Item Characterization of thin film Al/p-CdTe schottky diode(2008) Mahesha, M.G.; Kasturi, V.B.; Shivakumar, G.K.A study has been made on the behavior of Al/p-CdTe thin film junction grown by thermal evaporation method. I-V characteristics show that the Al makes Schottky contact with p-CdTe. The variation of junction capacitance with frequency and voltage has been studied to evaluate the barrier height. The activation energy and band gap have been estimated by studying variation of resistivity with temperature. Using all these data, band diagram of Al/p-CdTe has been proposed. © TÜB?TAK.Item Phase transformation, structural evolution, and mechanical property of nanostructured feal as a result of mechanical alloying(Springer New York LLC barbara.b.bertram@gsk.com, 2009) Rajath Hegde, M.M.R.; Surendranathan, A.O.The objective of the work is to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrates on the synthesis, characterization, and structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics are prepared directly by MEA in a high-energy ball mill. Milling is performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al are progressively transformed into a partially disordered solid solution with an average composition of Fe-50 at.% Al. Phase transformation, structural changes, morphology, particle size measurement, and chemical composition during MEA are investigated by X ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS). Vickers microhardness (VMH) indentation tests are performed on the powders. The XRD and SEM studies reveal the alloying of elemental powders as well as transition to nanostructured alloy; crystallite size of 18 nm is obtained after 28 h of milling. Expansion/contraction in lattice parameter accompanied by reduction in crystallite size occurs during transition to nanostructured alloy. Longer milling introduces ordering in the alloyed powders as proved by the presence of superlattice reflection. Elemental and alloyed phases coexist while hardness increases during MEA. copy2009 Springer Science+Business Media, Inc.Item Thermal contact at solder/substrate interfaces during solidification(2009) Nyamannavar, S.; Prabhu, K.N.Heat flux transients at the solder/substrate interface during the solidification of Sn-37Pb and Sn-3.5Ag solder alloys against metallic substrates were estimated by the lumped heat capacitance model and the contact condition was assessed by scanning electronic microscopy (SEM). Copper substrates yielded maximum contact heat flux followed by brass and aluminium substrates. The SEM study in the solder/substrate interfacial region revealed the existence of a clear gap with the aluminium substrate. A conforming contact was obtained with copper and brass substrates. © 2009 Institute of Materials, Minerals and Mining.Item Finite element analysis of open die extrusion of al-5zn-1mg alloy; Analiza izguravanja legure al-5zn-1mg kroz otvoreni kalup pomo]u kon?nih elemenata(2009) Geethalakshmi, K.; Srinivasan, K.In this work, an effort has been made to study the open die extrusion of Al-5Zn-1Mg alloy using finite element analysis. The two basic parameters of open die extrusion, i.e., die included angle and the extrusion strain are varied to find the corresponding limiting strain values. Effect of main parameters on the open die extrusion is analyzed, and the limiting range of deformation is obtained. The results obtained are verified by means of contrasting with the experimental data. Pure open die extrusion is found to be possible for extrusion strain (relative strain during extrusion) up to 0.28. However, as the extrusion strain increases from 0.09 to 0.28, upsetting dominates over pure extrusion on varying the die angle from 12° to 40°.Item Enhancement of heat transfer characteristics of transformer oil by addition of aluminium nanoparticles(2011) Rajesh, E.; Prabhu, K.N.A two step approach involving the synthesis of Al nanoparticles by mechanical milling followed by dispersion of the nanoparticles in the base fluid is adopted in the present work to prepare transformer oil based nanofluids. Stainless steel (AISI 304) probes of diameter 15 mm and height 70 mm were used to determine the cooling rate intensities of nanofluids. Heat transfer coefficients were determined using Kobasko's method. A dynamic contact angle analyzer was used to determine the contact angle of the droplet on the substrate. The addition of Al nanoparticles to the base fluid decreases the wettability and improves its heat transfer capability. The vapour phase stage existed for a longer period of time for transformer oil than for Al-transformer oil based nanofluids. The dispersion of nanoparticles in the base fluid is believed to disrupt the vapour blanket stage in the early stage of the cooling process. The peak heat transfer coefficient increases with an increase in the Al nanoparticle content in the oil. The addition of 0.5 vol % nanoparticles enhances the peak heat transfer coefficient by about 70 %. Copyright © 2011 by ASTM International.Item Corrosion inhibition of 6061 Al-15 vol. pct. SiC(p) composite and its base alloy in a mixture of sulphuric acid and hydrochloric acid by 4-(N,N-dimethyl amino) benzaldehyde thiosemicarbazone(2011) Geetha, G.M.; Nayak, J.; Nityananda Shetty, A.N.The corrosion inhibition characteristics of 4-(N,N-dimethylamino) benzaldehyde thiosemicarbazone (DMABT) on the corrosion behavior of 6061 Al-15 vol. pct. SiC(p) composite and its base alloy were studied at different temperatures in acid mixture medium containing varying concentrations of hydrochloric acid and sulphuric acid using Tafel extrapolation technique and ac impedance spectroscopy (EIS). The effect of inhibitor concentration, temperature and concentration of the acid mixture media on the inhibitor action was investigated. It was found that inhibition efficiencies increase with the increase in inhibitor concentration, but decrease with the increase in temperature and with the increase in concentration of the acid media. Thermodynamic parameters for dissolution process were determined. The adsorption of DMABT on both the composite and base alloy was found to be through physisorption obeying Freundlich adsorption isotherm. © 2010 Elsevier B.V. All rights reserved.Item Influence of Ti, B and Sr on the microstructure and mechanical properties of A356 alloy(2011) Mallapur, D.G.; Kori, S.A.; Udupa, K.R.In the present investigation, the microstructural and mechanical properties study of A356 alloy have been discussed. The microstructural aspect of cast A356 alloy employed in the present study is strongly dependent on the grain refinement (Ti and B) and modification (Sr). The mechanical properties such as PS, UTS, %E, %R, YM and VHN have been investigated. This paper deals with the combined effect of grain refinement and modification, which improves the overall mechanical properties of the alloy. It is also a well-known fact that the mechanical properties of cast A356 alloy were improved by subjecting suitable melt treatment such as grain refinement, modification and mould vibration, etc. The quality of castings and their properties can be achieved by refining of ?-Al dendrites in A356 alloy by means of the addition of elements such as Ti and B which reduces the size of a-Al dendrites, which otherwise solidifies with coarse columnar a-Al dendritic structure. In addition, modification is normally adopted to achieve improved mechanical properties. Metallographic studies reveal that the structure changes from coarse columnar dendrites to fine equiaxed ones on the addition of grain refiner and further, plate like eutectic silicon to fine particles on addition of 0.20% of Al-10Sr modifier. The present result shows that a reduction in the size of a-Al dendrites, modification of eutectic Si and improvement in the mechanical properties were observed with the addition of grain refiner Al-3Ti, Al-3B and modifier Al-10Sr either individual addition or in combination. The change in the microstructure from coarse columnar ?-Al dendrites to fine equiaxed dendrites and plate like eutectic silicon to rounded particles leads to improved mechanical properties. © Springer Science+Business Media, LLC 2010.