Faculty Publications
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Item Effect of ECAP on sliding wear behaviour of Mg-Zn-Gd-Zr alloy(Elsevier Ltd, 2020) Patil, A.; Bontha, S.; Ramesh, M.R.Magnesium is a lightweight, recyclable, and biocompatible material. However, the extensive commercial use of Magnesium and its alloys is hindered by their poor wear behaviour and mechanical properties. Equal Channel Angular Pressing (ECAP) is a severe plastic deformation technique which improves the material properties through grain refinement. In the present study, wear behaviour of ECAP processed Mg-Zn-Gd-Zr alloy was investigated. ECAP process was carried out up to 3 passes at a temperature of 380 °C. Wear testing of as-cast and ECAP processed alloy were carried out using dry sliding wear method on a pin on disk tribometer by varying loads. The wear mechanism was analysed using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Average Coefficient of Friction (COF) increased after each pass of ECAP. Wear rate increased with the applied load. Despite severe plastic deformation, wear resistance of ECAP processed samples was found to be lower than that of as-cast samples at higher loads. Abrasive and oxidation wear mechanisms were found in both as-cast and ECAP processed samples. © 2019 Elsevier Ltd. All rights reserved.Item Assessment of corrosion behavior of ductile irons by factorial experiments(2009) Surendranathan, A.O.; Prabhu, K.N.; Sudhaker Nayak, H.V.The corrosion behavior of unalloyed and alloyed ductile irons (as cast, annealed, and cold worked) in sea water, dilute sulfuric acid, and dilute sodium hydroxide solutions was assessed. Specimen history had a significant effect on the corrosion potential except in ductile iron alloyed with Ni. When the specimens were subjected to different levels of cold working, the corrosion rate was influenced by both the history and the medium. Temperature had a significant effect on the corrosion rate except in the case of unalloyed ductile iron. Factorial experiments indicated that the cold-worked samples were more sensitive to the effect of temperature and composition on the corrosion rate as compared to annealed and as-cast samples. The medium had a significant effect on the corrosion rate in all the cases. © 2009 ASM International.Item Studies on the influence of grain refining and modification on microstructure and mechanical properties of forged A356 alloy(Elsevier Ltd, 2011) Mallapur, D.G.; Udupa, K.R.; Kori, S.A.Microstructure and mechanical properties of the forged A356 alloy have been investigated in this paper. Results reveals that at micro level forged structure was more refined than as in the as cast conditions. This is due to the work hardening effect, where the original structure is destroyed during the forging and recrystallization helped in creating large number of nucleating sites leading to fine grain structure. From the investigations on the mechanical properties, we deduce that the PS, UTS and hardness of forged materials are obviously higher than those of the ones treated with as cast condition without and with the addition of grain refiners and modifier. © 2011 Elsevier B.V.Item Analysing the combined effect of crystallographic orientation and grain refinement on mechanical properties and corrosion behaviour of ECAPed ZE41 Mg alloy(National Engg. Reaserch Center for Magnesium Alloys, 2020) Sekar, S.; Narendranath, S.; Desai, V.Two step equal channel angular pressing carried out on as cast ZE41 Mg alloy resulted in a remarkable grain refinement. As compared to grain size of 46 µm in as cast sample, refinement upto 2.5 µm was achieved after 8th pass equal channel angular pressing (ECAP). The combined effect of crystallographic orientation and grain refinement was investigated by analysing the mechanical properties and corrosion behaviour of ZE41 Mg alloy using electron back scattered diffraction (EBSD). The first stage comprises of 1st, 2nd, 3rd and 4th passes at a processing temperature of 300 °C while the 5th, 6th, 7th and 8th passes were ECAPed at 275 °C in second stage. The mechanical properties of ZE41 Mg 158 yield tensile strength (YTS), 230 ultimate tensile strength (UTS) and 7% elongation in as cast condition is enhanced to 236 YTS, 295 UTS and 19.76%, respectively, after first stage ECAP. The yield tensile strength deteriorated due to the effect of texture predominating grain refinement during the second stage ECAP. The corrosion resistance of ZE41 Mg was significantly enhanced by ECAP and is inferred from electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation results .The role of microstructure was minimal on corrosion behaviour of ZE41 Mg due to extra resistance when tested in 0 M NaCl. However, the influence of grain refinement greatly influenced the improvement in corrosion resistance of ZE41 Mg rather than crystallographic orientation observed from EBSD. In contrast, the crystallographic orientation predominated the effect of grain refinement during ZE41 Mg corrosion in chloride containing (0.1 M and 1 M NaCl) solutions. From the observation of results it is found that equal channel angular pressing has the dual advantage of improving mechanical properties and corrosion resistance of ZE41 Mg alloy. © 2020Item 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 Effect of zirconium oxide particulate composites with Al-Si on the microstructural and mechanical properties of hot pressed, spray forming and stir casting methods(Taylor and Francis Ltd., 2023) Patil, I.S.; Anarghya, A.; Rao, S.S.; Herbert, M.A.; Kushwaha, R.This research work aims to investigate the aluminum and silicon alloy reinforced with the ZrO2 powder particles, which has been fabricated using stir casting and spray deposition method. The mechanical properties, micro hardness and microstructure of the developed metal matrix composite is investigated. The microstructural results indicate that the rich interface among the AlSi-ZrO2 particles and depicts the agglomeration of reinforced phase resulting to poor wettability of ZrO2 and observed decohesion. The mechanical testing results indicate that the tensile strength increases with the percentage of ZrO2. Moreover, as cast composites exhibit reverse tendency in compressive and hardness values. The highest compressive values for as cast and hot-pressed composites were 380 MPa and 337 MPa for 10% ZrO2. The highest tensile strength of 191.83 MPa was obtained for 5% ZrO2 as cast composite and 164 MPa for 15% ZrO2 hot pressed composite. It is to note that as cast composite method represented more homogenous data compared to the hot-pressed composites. Hot pressed samples exhibited the reduction in the porosity compared to the as cast. The developed method proved to be accurate, reduced time and efficient to predict the numerous samples. © 2021 Engineers Australia.Item Influence of friction stir processing on microstructure, mechanical properties and corrosion behaviour of Mg-Zn-Dy alloy(Springer, 2023) Rokkala, U.; Bontha, S.; Ramesh, M.R.; Balla, V.K.In the present study, friction stir processing (FSP) was carried out on as-cast Mg-Zn-Dy alloy to tailor grain size and texture which alter the mechanical properties and corrosion behaviour. The grain size of the as-cast alloy was reduced from 60 ± 2 µm to 3 ± 0.1 µm after FSP due to dynamic recrystallization. The effect of grain size, crystallographic orientation and fine precipitates on mechanical properties were investigated using field emission scanning electron microscope (FESEM) and electron back scattered diffraction (EBSD). The ultimate tensile strength, yield strength, % elongation and hardness of FSPed alloy improved by 55%, 60%, 53% and 46% when compared to as-cast alloy. The FSPed Mg-Zn-Dy alloy exhibited a 79% decrease in corrosion rate when compared to as-cast alloy which can be attributed to grain refinement, uniform distribution of secondary precipitates and strong basal texture. The surface of FSPed sample after immersion corrosion exhibited calcium phosphate rich minerals which help in apatite formation on the sample surface. Cytotoxicity studies using MTT assay revealed more than 80% cell viability for both as-cast and FSPed alloy illustrating non-toxic nature of both the samples. The results of this study indicate that FSPed Mg-Zn-Dy alloy is a potential material for biodegradable implants due to its high strength, corrosion resistance and biocompatibility. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.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 Microstructural Evolution of Mg-Zn-Gd Alloy Using Equal Channel Angular Pressing to Enhance Mechanical and Corrosion Properties(Springer, 2025) Rokkala, U.; Patil, A.; Bontha, S.; Ramesh, M.R.; Balla, V.K.; Srinivasan, A.Equal channel angular pressing (ECAP) was used on the Mg-Zn-Gd alloy in this study to improve its corrosion and mechanical properties. Microstructural and phase analysis reveal that, after ECAP, a substantial grain refinement occurred, and secondary phases were observed. The grain size of the as-cast (AC) sample is reduced from 20 ± 1 to 0.88 ± 0.6 µm, attributed to dynamic recrystallization. The mechanical properties of the ECAP sample were significantly improved when compared to the AC sample. An improvement in the microhardness (43%), ultimate tensile strength (73%), yield strength (76%), and ductility (50%) were observed for the ECAP sample. A decrease in the corrosion rate was observed for ECAP sample (9 ± 1 mm/year) compared to the AC (16 ± 2 mm/year) sample. The grain refinement and crystallographic orientation of the ECAP samples contributed to the enhancement of corrosion resistance. © ASM International 2025.