Browsing by Author "Udaya Bhat, K."

Now showing 1 - 20 of 41

A study on HAZ behaviour in 800 MPa cold rolled and hot rolled steel weld
(Elsevier Ltd, 2021) John, M.; Perka, P.; Udaya Bhat, K.; Bhat Panemangalore, D.
In the automotive sector, the demand for advanced high strength steels (AHSS) is increasing day by day. Based on the application, cold rolled and hot rolled steels are used for various components in a vehicle body. Typically, cold-rolled grades with dual-phase, DP780 steel is used in the form of welded blanks. Hot rolled grades with Ti-Nb microalloy content, like HS800 steel are used in as long members. Welding is an important step to be considered in the design of materials for mass production as required in the automobile sector. In this investigation, Pulsed Gas Metal Arc Welding (P-GMAW) is carried out on both steels with a solid filler wire of strength 800 MPa. Static tensile tests indicated that failure in both steels welds occurred in the heat-affected zone region. The crack initiation and propagation behaviour were compared in both steels. In DP780 steels, the presence of the acicular ferrite and acicular martensite resisted the crack initiation and propagation in the weld region whereas, the chaotic nature of the acicular ferrite in HS800 steel. Microstructural studies revealed that the reason for heat affected zone (HAZ) failure in HS800 steel is due to the presence of hard TiN particles with a size of more than 1 Âµm which causes decohesion in the matrix. In DP780 steel failure is due to the presence of tempered martensite in the subcritical heat affected zone (SCHAZ). This study divulges the influence of filler wire chemistry, dilution, and welding parameters on cold rolled and hot rolled AHSS steels used in the automotive industry. Â© 2021 Elsevier Ltd. All rights reserved.
AHSS welding using undermatching filler wires and process advantages with P-GMAW
(Elsevier Ltd, 2021) John, M.; Perka, P.; Udaya Bhat, K.
The major challenge during welding of advanced high strength steels (AHSS) is finding an appropriate low cost filler wire which minimizes the softening in the heat affected zone (HAZ). The fabricators always prefer undermatching wires to join the thinner sections. This study reports the differences in the microstructure and mechanical properties of Ti-Nb microalloyed steel prior welded using pulse gas metal arc welding (P-GMAW) and standard gas metal arc welding (GMAW). The results indicate that the microalloyed steel welded using P-GMAW has inherent advantage over the standard GMAW. The pulses intensified the vibration perturbation in the weld puddle which cause microstructural refining and increased formation of the acicular ferrite (AF) constituent. The higher percentage of AF present in the weldment resisted propagation of the crack during static tensile test. Microhardness, ultimate tensile strength and joint efficiency during P-GMAW are much higher than the samples welded by standard GMAW. Â© 2021 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the Global Conference on Recent Advances in Sustainable Materials 2021.
Carbon Nanomaterials for Biofuel Cells
(wiley, 2023) Udaya Bhat, K.; Bhat Panemangalore, B.P.
With the increase in energy demands, an incentive is given for scientific research towards providing sustained supply of energy to mankind. Among several alternative fuels, biofuel cells are an emerging field that is given a major impetus. Using a biological and chemical process to produce clean and efficient electrical energy can reduce the usage of to-be extinct fossil fuels. To facilitate these processes, enzymes and microbes play a very important role in transfer of electrons around the electrolyte and across electrodes. Several plant and animal-based products can be used and they are discussed. Among different materials used to synthesize biofuel cells, this chapter primarily discusses carbon-based nanomaterials which are attractive due to many significant properties it exhibits. Several such materials exist like graphite, carbon nanoparticles, nanotubes, nanohorns, nanorods that differ in morphology and presents remarkable opportunities to design and fabricate different varieties of biofuel cells. The composition and power densities of various biofuel cells are presented along with its several applications like in vivo implantation, energy extraction from body fluids and fruits. Smart textiles, self-powered biosensing applications of these biofuel cells suggest that research in this direction is an endless frontier. © 2021 Scrivener Publishing LLC.
Characterization of DC Magnetron Sputtered Copper Thin Film on Aluminium Touch Surface
(Springer, 2019) Augustin, A.; Rajendra Udupa, K.; Udaya Bhat, K.
Hospital care-assisted infections introduce problems like prolonged hospital stay, additional financial burden and higher death rate. Since copper is registered by US Environmental Protection Agency as the only solid antimicrobial metal, it could be used in hospital touch surfaces. In the present work, copper has been deposited on the aluminium substrate by DC magnetron sputtering method with different target power. Prior to the coating, the substrate has undergone double zincation process. The coating has been characterized by XRD, SEM, TEM, scratch hardness test and microhardness test. From the TEM micrographs, the grain size has been found to decrease from 49 to 18 nm on increasing the deposition power from 50 to 150 W. Along with the decrease in the grain size, the mechanical properties like scratch hardness and microhardness of the coating have been increased. The preferred growth along [111] direction observed in XRD analysis is responsible for the increase in the hardness of the coating apart from the presence of the nano-grains. The SEM image of the coating shows nodular morphology which enhances the surface area. © 2019, The Indian Institute of Metals - IIM.
Compositionally modulated multilayer Cu-Zn alloy coatings fabricated using eco-friendly non-cyanide pulse electrochemical deposition
(Elsevier Ltd, 2023) Bharadishettar, N.; Kumar, K.; Udaya Bhat, K.
Pulse electrodeposition of Cu-Zn compositional modulated multilayer alloy (CMA) coatings was carried out onto AISI 304 stainless steel substrate using an environmentally friendly alkaline non-cyanide electrolytic bath. Cu-Zn alloy multilayer coating was co-electrodeposited using a trapezoidal pulse current. Multilayer coatings can have two different metals in layers or two-phase mixtures. Different sets of multilayers of 10, 20, 50, and 100 were done using a trapezoidal pulse current. In the trapezoidal pulse current module, during the higher current stage (0.1 A) Zn was deposited as compared to the lower current module (0.02 A) where Cu was deposited. Microstructural and structural analysis of the coatings confirmed nanocrystalline morphology with peaks corresponding to crystallographic planes of (002), (111), (020), and (022). Deposited coatings are hydrophilic in nature. The microhardness of the coatings is decreased with an increase in the number of layers deposited. Â© Â© 2023 Elsevier Ltd. All rights reserved.
Controlled crystallisation of thermal evaporated GST-on-SOI for photonic neuromorphic application
(Optica Publishing Group (formerly OSA), 2021) Kallega, R.; Shekhawat, R.; Udaya Bhat, K.; Ramesh, R.; Selvaraja, S.K.
In this paper, we demonstrate controlled phase tuning of thermally evaporated germanium antimony telluride (GST) integrated silicon ring-resonator for potential neuromorphic application. We present and correlate electrical and photonic phase transition of ring integrated GST. Â© OSA 2021.
Degradation response and bioactivity assessment of antimicrobial copper coatings in simulated hand sweat environment
(Elsevier B.V., 2022) Bharadishettar, N.; Udaya Bhat, K.
The antimicrobial copper coatings were deposited on AISI 304 stainless steel (SS) using electrodeposition technique for touch surface applications. Electrodeposition was performed using a non-cyanide electrolyte, with varying copper concentrations. The copper coatings were investigated for their microstructure, in vitro degradation in the simulated hand sweat environment, and antimicrobial activity in an agar medium. It is noted that all the coatings have nanostructures in their microstructure. The microstructure of the coatings along with the contact period with the bacteria affects the antimicrobial activity measured against Escherichia coli and Staphylococcus aureus. The nanostructured morphology has resulted in an increased surface area with enhanced copper toxicity. The degradation behavior of coatings in the simulated hand sweat solution was further probed using potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). © 2022 Elsevier B.V.
Dry sliding wear behaviour of Al-5Zn-2Mg alloy processed by severe plastic deformation
(Elsevier Ltd, 2019) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.
Equal channel angular extrusion/pressing (ECAE/P) is an effectual technique to raise the mechanical, physical properties and resistance to wear of the materials. In this research, Al-5Zn-2Mg alloy material was ECAPed in route BC at lowest temperature. Hardness of the test material was increased after ECAE/P due to microstructure refinement. To demonstrate the wear characteristics of the Al-5Zn-2Mg alloy material after ECAE/P, wear tests (in dry sliding condition) were conducted at 2 conditions (condition 1: 19.62 N load and 1 m/s sliding speed, condition 2: 39.24 N load and 2 m/s sliding speed). The wear rate and magnitude of coefficient of friction (Î¼) were lessened after ECAE/P. Abrasive, adhesive and oxidation wear mechanisms are the predominant wear mechanisms noticed in the ECAE/P processed billets. Along with these mechanisms relocation of iron elements from the counter body (disc) to the test material was noticed. Â© 2019 Elsevier Ltd.
Effect of acid pickling treatment of stainless steel substrate on adhesion strength of electrodeposited copper coatings using non-cyanide electrolyte
(Elsevier Ltd, 2023) Bharadishettar, N.; Udaya Bhat, K.
In recent years, copper-based antimicrobial coatings have gained popularity in healthcare and public recreation facilities. The morphology, topography, and adhesion strength are decisive properties for copper coatings to have long-term antimicrobial effectiveness in hospital environments. This work explores the effect of multistage acid pickling treatment of AISI 304 stainless steel substrate on the adhesion strength of the copper coating. The copper coating was obtained by electrodeposition using an alkaline non-cyanide electrolyte. After the fourth stage of acid pickling, the copper coating had an excellent adhesion strength, up to 9 MPa. Glow discharge optical emission spectroscopy (GDOES) examination revealed no oxide scales or other contaminants on the SS surface after the fourth (final) stage of acid pickling. Using a non-contact optical profilometer, it was observed that the roughness of the substrate increased with each stage of the pickling treatment. The surface topography analysis confirms the increased density of the interlocking sites, which favors the adhesion of the coating. On the other hand, the microstructure of the copper coating showed a cauliflower-like morphology with an average nodule size of 28 nm. Transmission electron microscopy confirmed that the coatings have nano-scaled crystallites with internal twins inside the grains of copper coatings. © 2023 Elsevier Ltd
Effect of heat treatment on structure and properties of multilayer zn-ni alloy coatings
(International Association of Physical Chemists, 2013) Rao, V.R.; Hegde, A.C.; Udaya Bhat, K.
Composition modulated multilayer alloy (CMMA) coatings of Zn-Ni were electrodeposited galvanostatically on mild steel (MS) for enhanced corrosion protection using single bath technique. Successive layers of Zn-Ni alloys, having alternately different composition were obtained in nanometer scale by making the cathode current to cycle between two values, called cyclic cathode current densities (CCCD’s). The coatings configuration, in terms of compositions and thicknesses were optimized, and their corrosion performances were evaluated in 5 % NaCl by electrochemical methods. The corrosion rates (CR)’s of multilayer alloy coatings were found to decrease drastically (35 times) with increase in number of layers (only up to 300 layers), compared to monolayer alloy deposited from the same bath. Surface study was carried with SEM, while XRD was used to determine metal lattice parameters, texture and phase composition of the coatings. The effect of heat treatment on surface morphology, thickness, hardness and corrosion behaviour of multilayer Zn-Ni alloy coatings were studied. The significant structural modification due to heat treatment is not accompanied by any decrease in corrosion rate. This effect is related to the formation of a less disordered lattice for multilayer Zn-Ni alloy coatings. © 2013 by the authors; licensee IAPC, Zagreb, Croatia.
Effect of retrogression and re-ageing heat treatment on microstructure and microhardness of aluminium 7010 alloy
(EDP Sciences edps@edpsciences.com, 2018) Nandana, M.S.; Udaya Bhat, K.; Manjunatha, C.M.
Aluminium alloy 7010 is subjected to retrogression and re-ageing (RRA) heat treatment to study the influence of microstructural changes on hardness. Retrogression is performed at 190 Â°C for different time intervals ranging from 10 to 60 minutes. Optimum time for retrogression treatment is estimated based on the retrogression time that result with equivalent mechanical properties as that of peak aged (T6) condition. Retrogression performed for 30 minutes resulted with micro hardness of 203 HV, which is equivalent to that obtained by following T6 treatment. Microstructural characterization done with the help of transmission electron microscope (TEM) indicates RRA treatment results with the coarsened and discontinuous precipitates along the grain boundary which is similar to over aged (T7) condition, where as fine and densely populated precipitates in the matrix similar to T6 condition. Coarse and discontinuous grain boundary precipitates (GBP's) improves resistance to stress corrosion cracking. Fine and dense precipitates in the matrix ensures hardness equivalent to that of T6. Â© The Authors, published by EDP Sciences, 2018.
Effect of Retrogression Heat Treatment Time on Microstructure and Mechanical Properties of AA7010
(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Nandana, M.S.; Udaya Bhat, K.; Manjunatha, C.M.
The effect of retrogression time during retrogression and re-aging (RRA) treatment of AA7010 is evaluated by performing tensile tests and characterizing the microchemistry of the grain boundary precipitates (GBPs) using transmission electron microscope coupled with the energy-dispersive spectroscopy. Retrogression time is evaluated so that the ultimate tensile strength of the RRA-treated sample is equal to that of the T6-treated sample and the grain boundary microstructure similar to that of the over-aged (T7451) condition. The investigation reveals that the sample retrogressed at 200 °C for 20 min has UTS of 586 MPa which is equivalent to that of the T6 sample and 11.5% higher than that of the T7451 condition. The fracture toughness of the RRA-treated sample was 41 MPa?m. Microstructure of the RRA-treated sample is similar to T7451, along the grain boundaries and in the grain interior similar to that of the T6-treated sample. Energy-dispersive spectroscopy confirmed the increment of Cu content on the GBP’s with increase in the retrogression time, which is expected to improve the stress corrosion cracking resistance of the alloy. © 2018, ASM International.
Effect of Samarium (Sm) Addition on Microstructure and Mechanical Properties of AA5083 Alloy
(Springer Science and Business Media Deutschland GmbH, 2024) Aravindh, G.; Kumar, G.V.P.; Udaya Bhat, K.
Researchers are interested in reaping the potential benefits of incorporating small amounts of rare earth elements into aluminum alloys to attain finer grain size and to improve mechanical properties like toughness. This research investigates the effects of samarium (Sm) addition at concentrations of 0.5%, 1.0%, and 1.5% by weight on the microstructural and mechanical properties of AA5083 alloy. Optical microscopy (OM), field emission gun scanning electron microscopy (FEGSEM), X-ray diffraction (XRD), tensile testing machine (UTM), Vickers microhardness testing, and Charpy instrumented impact test were employed to evaluate the microstructure and mechanical properties of both as cast and solution treated (ST) samples. The samarium (Sm) is a beneficial grain refiner, leading to tailored properties in the AA5083 alloy. The results indicate that adding 1 wt% Sm generated significant enhancements in mechanical properties, such as tensile strength increased by 236 MPa and an elongation of 13.1% with a 27% reduction in grain size. However, incorporating 1.5 wt% Sm had an adverse impact on material properties, such as the grain size of the material increased by 22.73% and reduction in the tensile strength by 31%, corresponding to 1 wt% Sm added AA5083 alloy. Impact energy was reduced with the addition of Sm to the AA5083 alloy, both in as cast and ST samples. Furthermore, fractography was performed after impact and tensile testing. © American Foundry Society 2023.
Effect of wire feed rate on microstructure development during bead on plate welding of microalloyed steel using P-GMAW
(Elsevier Ltd, 2020) John, M.; Kumar, P.A.; Udaya Bhat, K.
Welding of advanced high strength steel has been challenging because of difficulties associated with retaining high strength and toughness in the weldment. In this investigation, Ti-Nb microalloyed 800 MPa steel was subjected to bead on plate welding trials using ER70S-6 filler wire. Synergic pulsed mode was used for welding. Here the system could optimize the welding current and voltage once the selection of wire feed rate was done. Analysis of weld bead was done by measuring the weld bead parameters, observing microstructural details and calculating microhardness values. The investigation indicates that 6 m/min wire feed rate produces good weld bead, minimum reinforcement and optimum dilution. The microstructure is predominantly acicular in nature and microhardness in weld and HAZ is higher compared to the beads produced using other wire feed rates. Â© 2020 Elsevier Ltd. All rights reserved.
Effect of zinc content on the microstructure and mechanical properties of Al-Zn-Mg alloy
(Elsevier Ltd, 2022) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.
In the present work, Aluminium-Zinc-Magnesium alloys (5 wt%, 10 wt% and 15 wt% Zinc and 2 wt% Magnesium) were prepared by casting process in a metal die. After casting process, heat treatment was conducted to the prepared alloys. To study the consequence of Zinc on the prepared alloys microstructure and mechanical properties were investigated. In as-cast state, in all three compositions, dendrite formation was noticed. While, after homogenization heat treatment, grain boundaries were noticed. Rise in the Zinc in the material leads to enhance the secondary particles. Microhardness and tension experiments were conducted to investigate the mechanical properties. Rise in the Zinc in the material leads to enhance the microhardness and tension strength. But ductility of the material declined with rise in the Zinc in the material. © 2021
Enhancement of Microstructural, Mechanical, and Tribological Properties of AA5083 Alloy via Multi-axial Forging
(Springer, 2025) Aravindh, G.; Sahoo, B.; Kumar, G.V.P.; Udaya Bhat, K.
The present study investigates the influence of multi-axial forging (MAF) on the microstructure, mechanical, and wear properties of the AA5083 alloy. After solution treatment, the alloy was subjected to three MAF cycles at room temperature with a strain of 0.63 per cycle. The evolution of the microstructure was analyzed using optical microscopy, field emission gun scanning electron microscopy, and x-ray diffraction. Mechanical properties were evaluated through tensile testing, and Vicker’s micro-hardness and wear behavior of the alloys were investigated using reciprocating wear tests. The results demonstrated significant improvement in properties after the third MAF cycle, forming 8.3 ?m wide shear bands and a refined grain structure. The alloy achieved maximum hardness (130 HV), tensile strength (334 MPa), and elongation to failure (8.01%), along with a reduced strain-hardening exponent (0.27). Wear resistance showed marked enhancement, with wear volume reductions of 36%, 49%, and 21% under 1, 2, and 4 N loads, respectively. Similarly, wear rates decreased by 64%, 49%, and 15% under the same loads. These findings emphasize the MAF process's effectiveness in enhancing the mechanical and wear properties of AA5083 alloy, indicating its potential for advanced material processing techniques. © ASM International 2025.
Enhancing the surface integrity characteristics of Al-Li alloy using face milling
(Elsevier B.V., 2022) Marakini, V.; Srinivasa Pai, P.; Udaya Bhat, K.; Thakur, D.S.; Achar, B.P.
This work presents the milling induced surface integrity investigation of Al-Li alloy. The effect of milling on the surface roughness, microhardness, microstructure, and residual stress is studied. Uncoated carbide inserts are used for milling due their superior hardness and greater life, when machining softer materials such as aluminium and its alloys. Results show that the minimum surface roughness (Ra = 0.043 µm) and maximum microhardness (216 HV) are achievable from the milling process, when compared with the roughness (Ra = 0.528 µm) and microhardness (180 HV) of the as-received material. Results indicate limited harm to alloy microstructure from the milling process and the presence of compressive residual stress induced from milling. The work finds scope for aerospace applications. © 2022 Elsevier B.V.
Evolution of Tribological Properties of Cast Alâ€“10Znâ€“2Mg Alloy Subjected to Severe Plastic Deformation
(Springer Science and Business Media Deutschland GmbH, 2020) Manjunath, G.K.; Preetham Kumar, G.V.; Udaya Bhat, K.
In the current investigation, tribological behaviour of the cast Alâ€“10Znâ€“2Mg alloy processed by severe plastic deformation (SPD) technique was studied. In this work, one of the SPD techniques, equal channel angular pressing (ECAP) was adopted as a processing tool. ECAP was carried out in route BC and processing was attempted at the lowest temperature. After ECAP, grain structure of the material was refined and considerable improvement in the microhardness of the alloy was perceived. Mainly, wear resistance of the alloy material was enhanced with successive ECAP passes. Coefficient of friction of the alloy material was decreased with successive ECAP passes. Wear resistance of the alloy was decreased with a rise in the applied load and the sliding speed. Both at low and high load condition, abrasive wear was noticed in as-cast and homogenized specimens. Whereas in ECAPed specimens, in addition to abrasive wear, oxidation wear and adhesive wear were observed in low load and it changes to abrasive wear at high load. In the ECAPed specimens, at low load transfer of iron particles from the steel disc surface to the specimen surface was identified. Â© 2020, Springer Nature Singapore Pte Ltd.
Flow Properties of Cast Al-Zn-Mg Alloys Subjected to Equal Channel Angular Pressing
(Institute of Physics Publishing helen.craven@iop.org, 2018) Manjunath, G.K.; Preetham Kumar, G.V.; Udaya Bhat, K.
Flow stress can be described as the stress necessary to continue deformation at any stage of plastic strain. The strength coefficient (K) and strain-hardening exponent (n) are the two important flow properties of the material. In the present work, flow properties of three different cast Al-Zn-Mg alloys processed by equal channel angular pressing (ECAP) were investigated. ECAP processing was carried out in a die having Î¦ = 120Â° and Î¨ = 30Â°. After ECAP processing, significant grain refinement and increase in the hardness was observed. Compression test was used to determine the flow properties of ECAP processed samples. Force-stroke data was recorded from the compression test. Flow curves were drawn by using force-stroke data. Strength coefficient and strain-hardening exponent were determined from the log-log plot of true stress-strain curves. Significant increase in the strength coefficient was observed after ECAP processing. Also, the strength coefficient is increased when the zinc content is increased in the alloy. Strain-hardening exponent was decreased with increase in the number of ECAP passes. Â© Published under licence by IOP Publishing Ltd.
Formability behaviour of ferritic and austenitic rolled Nb–Ti stabilized IF grade steel
(Springer, 2023) Satish Kumar, D.; Sambandam, S.; Udaya Bhat, K.
Recently, soft hot strip and hard hot strip produced through ferritic rolling are projected as a direct replacement to austenitic cold-rolled sheets for many forming applications. However, industrial hot-rolling mills, with final rolling thickness limitations cannot produce these thinner products and have to be subsequently cold-rolled to the desired application thickness and further annealed. Under ferritic rolling conditions, the hot-rolling temperature of these coils governs the final properties. The temperature difference in hot-rolled sheets generates the difference in the microstructure and texture of these coils after cold-rolling and annealing and variation in their formability behaviour. In the present work, an Nb–Ti stabilized IF grade steel was hot-rolled at two different temperatures in the ferritic regime and subsequently cold-rolled and annealed for structure-property comparison. As formability is an application-specific requirement, the annealed sheets were tested for different formability characteristics. Industrially rolled samples were tested for fracture criterion, stretch-flangeability, deep drawability and stretch formability through the formability limit diagram, hole expansion ratio, earing test and Erichsen cupping test respectively. These parameters were compared with those of the austenitic regime rolled sheets. High temperature ferritic rolled sheets show improved formability in all tests due to better r ˙ , higher n-value, low Δr and stronger gamma fibre maxima at 111<121>. Low temperature ferritic rolled sheets show the lowest Δr and improved n-value, but has reduced r ˙ and higher alpha fibre texture. High temperature ferritic rolled sheets show higher formability limits in uniaxial tension and low temperature ferritic rolled sheets in biaxial tension of the FLD curve. Various tests established that high temperature ferritic rolled sheets are best suited for deep drawing and stretching applications whereas low temperature ferritic rolled sheets should be preferred for stretch forming applications. © 2022, Indian Academy of Sciences.