Journal Articles
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Item Progress in spinodal decomposition of a Cu-32Ni-2Cr alloy subjected to quench?age and quench?work?age treatments have been studied through hardness measurements as well as by X-ray diffraction techniques. It is found that recovery processes occur during early stages of aging which are interpreted in terms of the migration of matrix dislocations to interfaces. The kinetics of spinodal decomposition is found to be enhanced by prior deformation. Thermomechanical treatment results in a substantial increase in strength.(Publ by Carl Hanser Verlag GmbH & Co, Thermomechanical treatment of spinodal Cu-32Ni-2Cr alloy) Bhat, R.Raghavendra; Prasad Rao, P.1994Item 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 A simple method of characterizing local stress and local strain variation in metal working is suggested. It is an alternative to complex and time consuming visioplastic technique. A power law expression exists for hardness and strain similar to that of stress and strain. A linear expression relating hardness and stress has been estahlished. These are valid not only for pure metals but also for their alloys. © Meshap Science Publishers.(Hardness-stress-strain correlation in copper and brass through compression testing) Dharmaveera, N.; Srinivasan, K.1996Item This paper deals with an experimental investigation on the process of atmospheric plasma spraying of high performance ceramics such as Al2O3, Al2O3-TiO2, and PSZ on a steel substrate. The ceramic coatings were deposited under different spray conditions and optimal spray parameters were evaluated based on the quality of the coating judged in terms of bond strength and porosity. An expert system, using the above experimental data,developed in Borland C has been demonstrated.(Elsevier BV, Expert system for process optimization of atmospheric plasma spraying of high performance ceramics) Gowri, S.; Uma Shankar, G.; Narayanasamy, K.; Krishnamurthy, R.1997Item A heterogeneous process such as open die extrusion has been done on CP titanium and the extent of heterogeneity has been determined. The pressure for carrying out the process has been calculated theoretically, measured experimentally and calculated indirectly from hardness measurement in the deformation zone. Hardness-stress-train correlation is very useful here. A nomogram has been given so that knowing, ?, ?, ? and hardness, the punch pressure can be read off. It is a steady-reckoner that is very relevant for the shop floor in industry or the laboratory.(Elsevier Science S.A., Hardness-stress-strain correlation in titanium open die extrusion: an alternative to visioplasticity) Srinivasan, K.; Venugopal, P.1999Item The precipitation hardening of a Al-Zn-Mg-Al2O3(p) composite is explored. It is found that the peak hardness achieved is almost double that of precipitation hardening of Al-Zn-Mg alloy or dispersion strengthening of Al-Zn-Mg with 5% Al2O3(p). Toughness is marginally improved and tensile strength is one and half times that of precipitation hardened Al-Zn-Mg alloys. The ageing time for peak hardness is reduced due to acceleration of formation of precipitate. © Indian Academy of Sciences.(Indian Academy of Sciences, Precipitation hardening in Al-Zn-Mg-Al2O3(p) composite) Kiran, K.S.; Srinivasan, K.1999Item Effect of surface roughness on metal/quenchant interfacial heat transfer and evolution of microstructure(Elsevier Ltd, 2007) Prabhu, K.N.; Fernandes, P.In the present work, the effect of surface roughness on heat transfer rates in various quenchants was determined. The heat flux transients at the probe/quenchant interface were estimated by inverse modeling of heat conduction during end quenching of stainless steel probes with three different surface roughness (grooved, Ra = 3.0 and 1 ?m). Heat transfer during quenching was correlated with the hardness obtained for medium carbon AISI 1060 steel specimens. The effect of surface roughness on heat transfer rate during quenching in water and brine was significant for rough surface whereas its effect on heat transfer rate is only marginal in high viscosity oil quenchants. A fully martensitic structure was observed with grooved surface subjected to water quenching. With a smooth surface a mixed microstructure was obtained. The oil quenched specimens were found to be less sensitive to surface roughness. © 2005 Elsevier Ltd. All rights reserved.Item Thermal stability and high-temperature wear of Ti-TiN and TiN-CrN nanomultilayer coatings under self-mated conditions(Elsevier Ltd, 2007) Srinivasan, D.; Kulkarni, Trupti.G.; Anand, K.Ti-TiN and TiN-CrN nanomultilayers were thermally stable retaining uniform and sharp layer interfaces up to 24 h at 773 K, without any oxidation or phase transformation accompanying each individual layer. Decreasing the multilayer spacing resulted in an increase in the hardness in both cases. The coating hardness was found to be independent of the substrate type, when applied on HS718, Ti64 and HCHCr substrates. In scratch testing, the multilayers displayed a better resistance to the onset of failure, as compared to the monolayer TiN. The substrate plasticity played an important role in determining the coating failure mode. Self-mated wear tests revealed the CrN-TiN system to exhibit the best wear behaviour, both at room temperature and at 773 K. The Ti-TiN coatings are more accommodative with all three substrates, as compared to TiN-CrN and TiN. © 2006 Elsevier Ltd. All rights reserved.Item Investigations on the effect of ball burnishing parameters on surface hardness and wear resistance of HSLA dual-phase steels(2008) Rao, D.S.; Hebbar, H.S.; Komaraiah, M.; Kempaiah, U.N.Surface finish has a vital influence on most functional properties of a component like fatigue life, wear resistance, corrosion resistance, etc. This has given birth to processes such as lapping, honing, burnishing, etc. Burnishing is a fine finishing operation involving the cold working plastic deformation of surface layers to enhance the surface integrity and the functional utility of a component. The present study has been carried out to establish the effect of burnishing parameters viz. feed rate, speed, force, ball diameter and lubricant on surface hardness, and wear resistance of HSLA dual-phase steel specimens. The result indicates that burnishing parameters have significant effect on the surface hardness and wear resistance.Item Phase transformation, structural evolution and mechanical property of nanostructured FeAl as a result of mechanical alloying(2009) Rajath Hegde, M.M.R.; Surendranathan, A.O.Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrated on synthesis, characterization, structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics were prepared directly by MEA in a high energy rate ball mill. Milling was performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al were 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 were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS) respectively. Vickers micro hardness (VMH) indentation tests were performed on the powders. XRD and SEM studies revealed the alloying of elemental powders as well as transition to nanostructured alloy, crystallite size of 18 nm was obtained after 28 hours of milling. Expansion/contraction in lattice parameter accompanied by reduction in crystallite size occurs during transition to nanostructured alloy. Longer milling duration introduces ordering in the alloyed powders as proved by the presence of superlattice reflection. Elemental and alloyed phase coexist while hardness increased during MEA. © 2009 Allerton Press, Inc.