Browsing by Author "Shivaram, M.J."

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Development and Characterization of Biomedical Porous Ti–20Nb–5Ag Alloy: Microstructure, Mechanical Properties, Surface Bioactivity and Cell Viability Studies
(Korean Institute of Metals and Materials, 2022) Shivaram, M.J.; Arya, S.B.; Nayak, J.; Panigrahi, B.B.
Abstract: In this study, antibacterial Ag element added to synthesis of porous Ti–20Nb–5Ag (wt%) alloy using powder metallurgy space holder route. The microstructural, mechanical property, surface bioactivity and cytotoxicity behavior of porous Ti–20Nb–5Ag alloy have been investigated. The developed porous alloy obtained the porosities ranging from 22.5 to 68%. The porous sample having a porosity of about 43% is found to be in the optimum condition, which possess a modulus of about 5.8 GPa with an excellent compressive strength about 205 MPa. XRD result shows that the formation of small amount of α-Ti, β-Ti, along with α״ martensite and Ti2Ag are key phase constituents of sintered porous Ti–20Nb–5Ag alloys. The compression strength and elastic modulus of the sintered alloys were showed that decreased with increase of porosity. Surface bioactivity result revealed that the significant formation of hydroxyapatite on the alkali-heat treated (5 M NaOH) porous Ti–20Nb–5Ag alloy which is found after the in vitro test in SBF. Further, the cell viability test was conducted on as-synthesized porous Ti–20Nb–5Ag alloy for 1, 4, and 7 days using MG-63 human osteoblast cells and result shows an excellent cell proliferation, and the cytotoxicity test confirms the non-toxic nature of the porous alloy which is very much suitable for implant application. Graphic Abstract: [Figure not available: see fulltext.]. © 2021, The Korean Institute of Metals and Materials.
Electrochemical Corrosion and Impedance Studies of Porous Ti–xNb–Ag Alloy in Physiological Solution
(Springer, 2020) Shivaram, M.J.; Arya, S.B.; Nayak, J.; Panigrahi, B.B.
Porous titanium (Ti) and its alloys are promising materials for orthopedic applications due to their low elastic modulus, high strength, excellent corrosion resistance, and biocompatibility. In this study, the porous Ti–xNb–5Ag (x = 25, 30 and 35 wt%) alloys were synthesized using the powder metallurgy approach. The effects of Nb content on the porosity, mechanical properties, and electrochemical corrosion behavior of the alloys were investigated. XRD analysis revealed that the porous alloys mainly consist of ?-Ti, ?-Ti, intermetallic compound (Ti4Nb), and oxides of TiO2 and NbO phases. Porous alloys possess the porosity ranging from 57 to 65%, due to the addition of NH4HCO3 (45 wt%). Increase in Nb content lead to a reduction in the elastic modulus and compression strengths of the sintered porous Ti–xNb–5Ag alloys. All three developed porous Ti–xNb–5Ag alloys show the optimum combination of elastic modulus and compression strength, which is suitable for orthopedic applications. These porous alloys exhibit excellent electrochemical corrosion resistance in the simulated body fluids, and the samples having low porosity exhibit higher corrosion resistance than high-porosity samples. © 2020, The Indian Institute of Metals - IIM.
Influence of Multiaxial Cryoforging on Microstructural, Mechanical, and Corrosion Properties of Copper-Titanium Alloy
(2019) Ramesh, S.; Nayaka, H.S.; Sahu, S.; Gopi, K.R.; Shivaram, M.J.; Arya, S.
Multiaxial forging (MAF) was used to process Cu-4.5%Ti (wt.%) alloy at cryogenic temperature up to three cycles with a cumulative strain of 1.64. Microstructures, mechanical, and corrosion properties of as-received and deformed samples were analyzed. Microstructural analysis showed that average grain size decreased from 70 m to 200 nm, and electron backscattered diffraction (EBSD) analysis revealed the transformation of high-angle grain boundaries (HAGBs) to low-angle grain boundaries (LAGBs). Variations in intensity of peaks were observed by x-ray diffraction (XRD) technique. Microstructural investigation showed elongated grains with shear bands having width ~ 200 nm for 3-cycle sample. Tensile testing and micro-hardness tests showed improvements in ultimate tensile strength (UTS), yield strength (YS), and micro-hardness, with the increase in MAF cycles. Ultimate tensile strength and hardness increased from 605 MPa and 252 HV (for as-received) to 1284 MPa and 428 HV for three cycles of MAF-processed sample, respectively. Improvement in strength and hardness was attributed to refined grain structure. Corrosion study was carried out for different cycles of MAF-processed samples using potentiodynamic polarization, and corroded surfaces were analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis. 2019, ASM International.
Influence of Multiaxial Cryoforging on Microstructural, Mechanical, and Corrosion Properties of Copper-Titanium Alloy
(Springer, 2019) Ramesh, S.; Shivananda Nayaka, H.S.; Sahu, S.; Gopi, K.R.; Shivaram, M.J.; Arya, S.
Multiaxial forging (MAF) was used to process Cu-4.5%Ti (wt.%) alloy at cryogenic temperature up to three cycles with a cumulative strain of 1.64. Microstructures, mechanical, and corrosion properties of as-received and deformed samples were analyzed. Microstructural analysis showed that average grain size decreased from 70 µm to 200 nm, and electron backscattered diffraction (EBSD) analysis revealed the transformation of high-angle grain boundaries (HAGBs) to low-angle grain boundaries (LAGBs). Variations in intensity of peaks were observed by x-ray diffraction (XRD) technique. Microstructural investigation showed elongated grains with shear bands having width ~ 200 nm for 3-cycle sample. Tensile testing and micro-hardness tests showed improvements in ultimate tensile strength (UTS), yield strength (YS), and micro-hardness, with the increase in MAF cycles. Ultimate tensile strength and hardness increased from 605 MPa and 252 HV (for as-received) to 1284 MPa and 428 HV for three cycles of MAF-processed sample, respectively. Improvement in strength and hardness was attributed to refined grain structure. Corrosion study was carried out for different cycles of MAF-processed samples using potentiodynamic polarization, and corroded surfaces were analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis. © 2019, ASM International.
Processing and Characterization of Cu–10Sn/ZrO2 Alloys Processed Via Stir Casting Technique: Mechanical Properties and Wear Behavior Studies
(Springer Science and Business Media Deutschland GmbH, 2023) Nayak, P.H.; Ravi Prakash, M.; Vinay, V.; Srinivas, H.K.; Shivaram, M.J.
In this study, various amounts of nano-zirconia (ZrO2) were added as a reinforcement particle to synthesize Cu–10Sn–xZrO2 alloy using stir casting techniques. The mechanical and wear properties of metal matrix composites depend on the type of reinforcement material, morphological features and amount of the reinforcement material is added to matrix. The developed alloy obtained hardness ranging from 69 to 87 BHN for the addition of 0 to 12 wt% of nano-ZrO2 reinforcement particles. The ultimate tensile strength of developed alloys increased ranging from 271 MPa to 345 MPa, while yield strength showed 220 MPa to 263 MPa. Results indicate that ultimate tensile strength and yield strength of the reinforced alloys showed better mechanical properties than base alloy, which shows the significant influence of addition of reinforcement particles. The wear behavior of the developed alloys were examined using pin-on-disk tribometer. The developed reinforced alloys show that there was an increase in wear resistance with increasing the amount of nano-ZrO2 particles. However, results indicate that increase in wear rate with increase in applied load and sliding speed, with the increase in reinforcement particles showed better wear resistance at higher applied load and sliding speed as compared to base alloy. Microstructural features of the worn surface carried out using scanning electron microscopy (SEM). Worn surface analysis exhibits that wear resistance increases at 8 and 12 wt% of nano-ZrO2 particles. The prepared reinforced alloys exhibit excellent wear resistance, and hence, the developed reinforced alloys can be potentially used for various applications such as bearings and bushes. © 2022, American Foundry Society.
Role of porosity on electrochemical corrosion behavior of porous Ti-20Nb-5Ag alloy in simulated body fluid
(Elsevier Ltd, 2020) Shivaram, M.J.; Arya, S.B.; Nayak, J.; Panigrahi, B.B.
Porous titanium alloys are presently well-considered materials for orthopedic applications owing to their superior mechanical properties, excellent biocompatibility and high resistance to corrosion. Also, porous alloys are potentially minimizing the risk of stress-shielding effect as compared to bulk implant materials. In this present work focused to examine electrochemical corrosion behavior of porous Ti-20Nb-5Ag alloy (wt%) with different porosity levels. This designed alloy composition of elemental powders was mixed through mechanically alloying. The mechanically alloyed powder blended with four different amounts of NH4HCO3 (wt%), use to prepare the porous Ti-20Nb-5Ag alloy with porosity ranging from 22% to 68%. After the successful development of porous samples, we investigated the effect of porosity levels on electrochemical corrosion behavior of porous Ti-20Nb-5Ag alloys by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF) at 37 Â°C. The results show that an increasing the trend of porosity level causes a reduction of corrosion resistance. With increasing porosity, the corrosion current density increased and decreases the electrochemical polarization resistance in the SBF solution. Â© 2019 Elsevier Ltd. All rights reserved.
Tribocorrosion Behaviour of Biomedical Porous Ti–20Nb–5Ag Alloy in Simulated Body Fluid
(Springer Science and Business Media Deutschland GmbH, 2021) Shivaram, M.J.; Arya, S.; Nayak, J.; Panigrahi, B.B.
Porous Ti–20Nb–5Ag (wt.%) alloy was developed using powder metallurgy (PM) route with the porosity of 43% after sintering in a high vacuum atmosphere. The microstructure of the porous alloy revealed various micro, macro and interconnected pores with an average pore size of about 114 µm. Tribocorrosion behaviour of the porous alloy was examined in simulated body fluid under the various applied load of 1–10 N using DC electrochemical corrosion technique and kinetic parameters (corrosion potential, corrosion current density and breakdown potentials). After tribocorrosion test, the OCP values decreased from 0.17 to ? 0.49 VSCE as applied load was increased. The potentiodynamic polarization results revealed that the corrosion potential decreased, while corrosion current density increased under higher applied loads. Active–passive transition plots showed metastable passivity due to severe fluctuations of passive current density. After tribocorrosion, the surface morphology was analysed using SEM, and it exhibited the severity of wear tracks at higher applied loads. The results indicated that the developed porous Ti–20Nb–5Ag alloys exhibit better tribocorrosion properties in simulated body fluid. Through observations of SEM images of the worn surfaces, the visible scratches and deep grooves were observed along the sliding direction, indicating a predominant abrasive mechanism. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.