Journal Articles
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Item Microstructure Evolution in Cast Al-Zn-Mg Alloys Processed by Equal Channel Angular Pressing(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.In the present work, microstructure development and enhancement in the microhardness of Al-Zn-Mg alloys (with 5, 10, and 15% zinc) during equal channel angular pressing (ECAP) were investigated. Dendritic morphology was observed in the cast condition of all three alloys, and precipitates were situated along the inter-dendritic regions. After homogenization, precipitates in the inter-dendritic regions were uniformly distributed in the aluminum matrix and grain boundaries were developed. After 4 passes in route BC, large reduction in the grain size was observed. X-ray diffractometry showed that MgZn2 precipitate was developed in the ECAP-processed samples. Increase in the intensity of MgZn2 peaks was observed when the quantity of zinc is increased in the material. Also, changes in the intensity of XRD peaks were observed in ECAP-processed samples due to shear deformation. After ECAP, substantial increase in the microhardness was perceived. After four passes, microhardness increased to 109, 67, and 58% from the initial condition in A1, A2, and A3 alloys, respectively. Also, improvement in the microhardness was also observed when the quantity of zinc is increased in the material. © 2017, Springer Science+Business Media, LLC, part of Springer Nature and ASM International.Item 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.Item Microstructure and Mechanical Properties of Cast Al-5Zn-2Mg Alloy Subjected to Equal-Channel Angular Pressing(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Manjunath, G.K.; Preetham Kumar, G.V.P.; Udaya Bhat, K.; Huilgol, P.In the present work, cast Al-5Zn-2Mg alloy was processed through equal-channel angular pressing (ECAP) in route BC up to four number of passes. Microstructure and mechanical properties were investigated on processed and unprocessed materials. In cast condition, the material was composed of dendritic structure. After homogenization treatment, large-sized grains were observed. After ECAP processing, significant grain refinement was observed. After ECAP processing, high-density dislocations and high degree of misorientation between the grains were observed. In cast material, rod-shaped precipitates were observed, while, after ECAP processing, spherical-shaped precipitates were observed. ECAP processing leads to a noticeable improvement in the mechanical properties of the material. After four passes, 122% improvement in the microhardness and 135% improvement in the ultimate tensile strength of the material were observed. After three passes, a slight decrease in the mechanical properties was observed. This is attributed to the dissolution of the metastable ?? phase, annihilation of dislocations, dynamic recrystallization and texturing during ECAP processing. Brittle fracture mode was observed in tensile testing cast and homogenized samples. After ECAP processing, fracture mode was changed into shear fracture mode. © 2018, ASM International.Item 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. © 2021Item 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.Item Microstructure evolution in Al 6061 coating deposited on Al 2024 substrate by friction surfacing(Elsevier Ltd, 2022) Sudhish, R.; Udaya Bhat, K.In the present investigation, the microstructure evolution in Al 6061 coating deposited by friction surfacing on Al 2024 was studied in detail. The age hardening behaviour of the developed coating was also analysed. The Al 6061 tool material was solutionized prior to the coating process. The microstructural analysis revealed that, an ultra-fine grain microstructure could be achieved in coating by the coating process wherein the Al 2024 substrate has marginal modification in microstructure. Continuous dynamic recrystallization is identified as the mechanism of ultra-fine grain formation. Also, it was found that the process induced thermo-mechanical effect causing an increment in ageing kinetics. The enhanced ageing kinetics and formation of ultra- fine grains collectively improved the peak aged hardness of the friction surface coating, made using Al 6061. © 2022 Elsevier LtdItem 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.Item 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.Item Synergistic investigation on Fe[sbnd]N phases and gradient microstructure supported anti-indentation and anti-scratch performance of low-temperature plasma ion nitrided Ti[sbnd]Nb stabilized IF steel(Elsevier B.V., 2025) Sahoo, B.; Udaya Bhat, K.Plasma ion nitriding (PIN) is a remarkable surface modification process that utilizes a thermochemical environment to treat the substrate by diffusion-induced phenomena, allowing it to modify complex-shaped objects, especially steel components. However, the foremost shortcoming of PIN is the higher processing cost, which can be minimized by reducing the nitriding temperature. This leads to a prominent variation in the sample's microstructure, often resulting in a gradient microstructure in the depth direction, which can be beneficial for specific industrial applications like scratch resistance, abrasion resistance, etc. The current investigation performs an extensive study to extrapolate the gradient microstructure-induced indentation and scratch resistance of low-temperature PINed (400 °C to 500 °C) interstitial-free steel through microscopy, diffractometry, spectroscopy, microhardness test, indentation test, and scratch test (constant and progressive loading). The transmission electron microscopy and scanning electron microscopy findings suggested a clear trace of gradient microstructure containing various Iron nitride phases (?-Fe2-3N, ?'-Fe4N, and ??-Fe16N2), size and distribution of which affect the scratch resistance. The sample treated at 450 °C shows the best result, with an overall improvement in scratch hardness of 3.2 times the base value. The coefficient of friction, track depth, traction force variation, etc., are also studied and correlated with spectroscopy and microscopy findings. © 2025 Elsevier B.V.