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Poddar, C., Ningshen, S. & Jayamani, J. (2020). Corrosion assessment of Ni60 Nb30Ta10 metallic glass and its partially crystallized alloy in concentrated nitric acid environment. Journal of Alloys and Compounds, 813
Open this publication in new window or tab >>Corrosion assessment of Ni60 Nb30Ta10 metallic glass and its partially crystallized alloy in concentrated nitric acid environment
2020 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 813Article in journal (Refereed) Published
Abstract [en]

The corrosion resistance and passive film properties of Ni60Nb30Ta10 metallic glass and partially crystallized ribbon were investigated in 11.5 M nitric acid. The XRD study confirms the formation of nano-crystalline α-Ni in the amorphous matrix during crystallization at 650 °C under vacuum for 1 h. The electrochemical impedance spectroscopy, potentiodynamic polarization, and Mott-Schottky studies on the metallic glass exhibited higher corrosion resistance compared to the partially crystallized ribbon. XPS confirms the enrichment of Nb2O5 and Ta2O5 in the passive film of the glassy structure, while α-Ni is depleted in a partially crystallized alloy that affected the corrosion resistance.

Keywords
Metallic glasses, Semiconducting, Corrosion, EIS, SEM, XPS
National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31428 (URN)10.1016/j.jallcom.2019.152172 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Thirathipviwat, P., Song, G., Jayamani, J., Bednarcik, J., Wendrock, H., Gemming, T., . . . Han, J. (2019). A comparison study of dislocation density, recrystallization and grain growth among nickel, FeNiCo ternary alloy and FeNiCoCrMn high entropy alloy. Journal of Alloys and Compounds, 790, 266-273
Open this publication in new window or tab >>A comparison study of dislocation density, recrystallization and grain growth among nickel, FeNiCo ternary alloy and FeNiCoCrMn high entropy alloy
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2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 790, p. 266-273Article in journal (Refereed) Published
Abstract [en]

The microstructural evolutions in terms of dislocation density, annealing twin density as well as with respect to microstructural changes due to recrystallization and grain growth were investigated in pure Ni, equiatomic FeNiCo alloy, and FeNiCoCrMn high entropy alloy (HEA) during the thermomechanical process. All samples were single phase and showed a face-centered cubic (FCC) lattice structure. This was maintained during thermomechanical processing comprising of cold swaging by 85% reduction of cross-sectional area and subsequent annealing at 800 °C. The level of dislocation accumulation during cold swaging increased with the number of constituent elements. The FeNiCoCrMn HEA obtained the highest dislocation density, followed by the FeNiCo and Ni, respectively. After the annealing at 800 °C for 0.5 h, all samples achieved the large fraction of recrystallized grains with minor fraction of substructured grains and no deformed grain. The FeNiCoCrMn HEA obtained the smallest recrystallized grain size (∼5 μm) after the annealing at 800 °C for 0.5 h. This could be a result of the highest dislocation density generated during cold swaging prior to the annealing. The prolonged annealing at 800 °C for up to 24 h led to a grain growth for all the samples, however, at different growth rates. The FeNiCoCrMn HEA revealed the lowest rate of grain growth, but the microstructural changes during the annealing were not significantly different between the FeNiCo and Ni samples. Besides the effect of the number of constituent elements, the type and the combination of constituent elements have an effect on the microstructural evolution during the annealing.

Keywords
High entropy alloys, Dislocation density, Grain growth, EBSD, X-ray diffraction
National Category
Materials Engineering
Research subject
Steel Forming and Surface Engineering
Identifiers
urn:nbn:se:du-29833 (URN)10.1016/j.jallcom.2019.03.052 (DOI)000464663600032 ()2-s2.0-85063051522 (Scopus ID)
Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-12-20Bibliographically approved
Haribabu, S., Sudha, C., Raju, S., Hajra, R. N., Mythili, R., Jayamani, J., . . . Saroja, S. (2019). Effect of Al Addition on the Microstructure and Phase Stability of P91 Ferritic-Martensitic Steel. Metallurgical and Materials Transactions. A, 50(3), 1421-1436
Open this publication in new window or tab >>Effect of Al Addition on the Microstructure and Phase Stability of P91 Ferritic-Martensitic Steel
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2019 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 50, no 3, p. 1421-1436Article in journal (Refereed) Published
Abstract [en]

This paper presents the results of an experimental and computational study carried out to elucidate the effect of Al on the microstructure and phase stability of P91 F/M steel in as-cast, homogenized and normalized conditions. Al-added steels followed ‘Ferritic-Austenitic’ mode of solidification and the as-cast microstructures consisted of δ-ferrite + α′-martensite, the volume fraction of ferrite and hardness of martensite increased with Al concentration. Heat treatments and DSC experiments confirmed increased stability for δ-ferrite with Al addition. Systematic change in the phase transformations temperatures and volume fraction of equilibrium phases due to Al addition was estimated with the help of Thermo-Calc®. Al addition promoted the formation of AlN which was confirmed through electron microscopy-based investigations. AlN dissolution temperature was always above γ-loop which made it impossible to dissolve during austenization. With the help of Scheil and equilibrium simulations using Thermo-Calc®, elemental partitioning between δ-ferrite and α′ phases was found to be the reason for higher hardness of martensite. Based on experimental evidences, it is concluded that except in the case of 0.48 wt pct Al-added steel it is impossible to obtain single phase γ-field (without ferrite) at high temperature thereby a fully martensite structure on cooling.

National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31364 (URN)10.1007/s11661-018-5077-2 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Poddar, C., Jayamani, J., Ningshen, S. & Mudali, U. K. (2019). Effect of thermal oxidation on the oxide characteristic and corrosion behavior of Ni60Nb40 amorphous ribbon in nitric acid. Applied Surface Science, 479, 430-439
Open this publication in new window or tab >>Effect of thermal oxidation on the oxide characteristic and corrosion behavior of Ni60Nb40 amorphous ribbon in nitric acid
2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 479, p. 430-439Article in journal (Refereed) Published
Abstract [en]

The air-oxidation is a useful processing treatment to improve the corrosion resistance of Ni60Nb40 amorphous alloy. The oxidation kinetics of Ni60Nb40 amorphous ribbon follow two stage parabolic rate laws at 450 °C and 550 °C. The XPS analysis revealed that the surface of oxidized sample at 450 °C is enriched with Nb2O5, while oxidized sample at 550 °C, comprises of NiO and Ni2O3. The Mott-Schottky analyses confirmed the formation of n-type semiconducting film on the 450 °C oxidized sample in the nitric acid medium, while p-type semiconducting film on the 550 °C oxidized sample. Potentiodynamic polarization and EIS studies show that oxide film on the 450 °C oxidized sample exhibits highly protective barrier to the nitric acid when compared to the oxide film at 550 °C.

Keywords
Acid solution, EIS, Polarization, XPS, Semiconducting, Transpassivity
National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31400 (URN)10.1016/j.apsusc.2019.02.089 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Poddar, C., Jayamani, J., Amirthapandian, S. & Ningshen, S. (2019). Effect of thermally grown amorphous oxide film on the corrosion resistance properties of Ni50Zr25Nb25 metallic glass in nitric acid medium. Intermetallics (Barking), 113
Open this publication in new window or tab >>Effect of thermally grown amorphous oxide film on the corrosion resistance properties of Ni50Zr25Nb25 metallic glass in nitric acid medium
2019 (English)In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 113Article in journal (Refereed) Published
Abstract [en]

In the presents work, the effects of the surface oxidation of the Ni50Zr25Nb25 metallic glass on the corrosion behavior in nitric acid environment were investigated. The oxidation kinetics at 200 and 400 °C in air environment followed two-stage rate law. SEM and XPS investigation revealed the surface of thin (106 nm) amorphous oxide film composed of NiO, Ni2O3, ZrO2, and Nb2O5 when sample was oxidized at 200 °C. However, oxidation at 400 °C resulted in a thicker (721 nm) amorphous oxide film, enriched with only ZrO2 and Nb2O5. Potentiodynamic polarization results of the thermally oxidized metallic glass at 400 °C exhibited the wider passive range and significantly higher corrosion resistance in concentrated nitric acid when compared to the as-prepared and oxidized sample at 200 °C. After polarization at 2.2 V (Vs. Ag/AgCl), thermally oxidized sample at 400 °C exhibits smooth surface while the as-prepared MG undergoes a severe dissolution in 11.5 M nitric acid.

Keywords
Metallic glasses, Oxidation, Electrochemical corrosion, Oxide film, XPS, Nitric acid
National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31407 (URN)10.1016/j.intermet.2019.106571 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Poddar, C., Jayamani, J. & Ningshen, S. (2019). Passive film characteristics and corrosion behavior of thermally oxidized Ni60Nb30Ta10 metallic glass in nitric acid medium. Journal of Alloys and Compounds, 783, 680-686
Open this publication in new window or tab >>Passive film characteristics and corrosion behavior of thermally oxidized Ni60Nb30Ta10 metallic glass in nitric acid medium
2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 783, p. 680-686Article in journal (Refereed) Published
Abstract [en]

X-ray photoelectron spectroscopy (XPS) analyses confirmed the formation of different oxides upon thermal air oxidation (TO) of Ni60Nb30Ta10 metallic glass (MG) below the glass transition temperature. At 450 °C (450 TO-MG), surface of the oxide film was enriched with Nb2O5 (65%) and Ta2O5 (26%). Similarly, at 550 °C (550 TO-MG), the upper oxide layer was composed with NiO (67%), Ni2O3 (28.5%) and small fraction metallic Ni (4.5%). The electrochemical corrosion behavior of the thermally oxidized metallic glass samples was studied in 1, 6 and 11.5 M nitric acid at room temperature. Mott-Schottky analyses in nitric acid solutions confirmed the n-type semiconducting nature of the film for as-spun MG. On the other hand, the films formed on 450 TO-MG, and 550 TO-MG exhibited insulating and p-type, respectively. The donor (n-type) and acceptor (p-type) densities increases as the solution concentration increased. In nitric acid solutions, the current densities values obtained from potentiodynamic polarization studies indicated that 450 TO-MG exhibited higher corrosion resistance than the as-spun and 550 TO-MG samples.

Keywords
A. Metallic glasses, B. Rapid-solidification, C. Oxidation, C. Electronic properties, C. Corrosion, D. Photoelectron spectroscopies
National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31403 (URN)10.1016/j.jallcom.2018.12.335 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Jayamani, J., Ranjith, P. M., Ningshen, S. & Ramanathan, S. (2019). Studies on Corrosion of Titanium and Air-Oxidized Titanium in Fluorinated Nitric Acid. Transactions of the Indian Institute of Metals, 72(7), 1917-1926
Open this publication in new window or tab >>Studies on Corrosion of Titanium and Air-Oxidized Titanium in Fluorinated Nitric Acid
2019 (English)In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 72, no 7, p. 1917-1926Article in journal (Refereed) Published
Abstract [en]

Titanium (Ti) is a lustrous transition metal which possesses excellent corrosion resistance in several aggressive environments but is attacked by acidic fluoride media. In this work, the addition of fluoride ion to nitric acid on the corrosion behavior of Ti and air-oxidized Ti was studied. Air oxidation of Ti at 800 °C for 5 h resulted in the formation of an intact rutile TiO2 layer with a thickness of about 35 μm. The corrosion resistance was investigated from the polarization resistance ($$R_{\text{P}}$$RP) values which were obtained from linear polarization and electrochemical impedance spectroscopy (EIS) measurements. A decrease in the $$R_{\text{P}}$$RPvalue of Ti with the addition of fluoride ion in nitric acid was observed, and this indicated the formation of an unstable layer, which resulted in accelerated dissolution. The several order increase in the $$R_{\text{P}}$$RPvalue of air-oxidized Ti in nitric acid containing fluoride ions pointed the improved resistance to corrosion. The diffusivity of species through the air-oxidized TiO2 layer was estimated from the electrochemical equivalent circuit (EEC) analysis of EIS data. Even though the diffusivity increased by several orders with the addition of fluoride ions, air-oxidized Ti provided better protection against nitric acid containing fluoride ions than Ti. The corrosion rates of Ti and air-oxidized Ti in boiling nitric acid containing fluoride ions were also estimated from weight loss experiments. Even in boiling fluorinated nitric acid, air-oxidized Ti provided better corrosion protection, with corrosion rates of about 1000 times less than that of Ti.

National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31396 (URN)10.1007/s12666-019-01667-3 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Vetrivendan, E., Jayamani, J., Ningshen, S., Mallika, C. & Kamachi Mudali, U. (2018). Argon Shrouded Plasma Spraying of Tantalum over Titanium for Corrosion Protection in Fluorinated Nitric Acid Media. Journal of thermal spray technology (Print), 27(3), 512-523
Open this publication in new window or tab >>Argon Shrouded Plasma Spraying of Tantalum over Titanium for Corrosion Protection in Fluorinated Nitric Acid Media
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2018 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 512-523Article in journal (Refereed) Published
Abstract [en]

Argon shrouded plasma spraying (ASPS) was used to deposit a Ta coating on commercially pure Ti (CP-Ti) under inert argon, for dissolver vessel application in the aqueous spent fuels reprocessing plant with high plutonium content. Oxidation during plasma spraying was minimized by shrouding argon system. Porosity and oxide content were controlled by optimizing the spraying parameters, to obtain a uniform and dense Ta coating. The Ta particle temperature and velocity were optimized by judiciously controlling the spray parameters, using a spray diagnostic charge-coupled device camera. The corrosion resistance of the Ta coatings developed by ASPS was investigated by electrochemical studies in 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF. Similarly, the durability of the ASPS Ta coating/substrate was evaluated as per ASTM A262 Practice-C test in boiling nitric acid and fluorinated nitric acid for 240 h. The ASPS Ta coating exhibited higher corrosion resistance than the CP-Ti substrate, as evident from electrochemical studies, and low corrosion rate with excellent coating stability in boiling nitric, and fluorinated nitric acid. The results of the present study revealed that tantalum coating by ASPS is a promising strategy for improving the corrosion resistance in the highly corrosive reprocessing environment.

National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31394 (URN)10.1007/s11666-017-0678-7 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Jayamani, J., Nanda Gopala Krishna, D., Mallika, C. & Kamachi Mudali, U. (2018). Electrochemical Studies and XPS Analysis of the Surface of Zirconium-702 in Concentrated Nitric Acid With and Without Fluoride Ions. Transactions of the Indian Institute of Metals, 71(3), 521-531
Open this publication in new window or tab >>Electrochemical Studies and XPS Analysis of the Surface of Zirconium-702 in Concentrated Nitric Acid With and Without Fluoride Ions
2018 (English)In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 71, no 3, p. 521-531Article in journal (Refereed) Published
Abstract [en]

Zirconium exhibited pseudo-passive behavior in fluorinated nitric acid (11.5 M HNO3 + 0.05 M NaF) as the current density measured from the electrochemical studies was several orders higher than the value in fluoride free nitric acid. Impedance studies on zirconium sample exposed in 11.5 M HNO3 for 240 h confirmed the formation of the passive film with high polarization resistance value and the calculated thickness of the film based on the capacitance value was about ~4.5 nm. On the other hand, in fluorinated nitric acid, the charge transfer resistance value associated with the zirconium dissolution process was dominant when compared to that of the film formation. Results of X-ray photoelectron spectroscopic investigations upheld the presence of ZrOF2 and ZrF4 and indicated that the protective oxide layer growth was restricted by the presence of fluoride ions.

National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31395 (URN)10.1007/s12666-017-1165-z (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Jayamani, J., Thirathipviwat, P., Han, J. & Gebert, A. (2018). Microstructure, mechanical and thermal oxidation behavior of AlNbTiZr high entropy alloy. Intermetallics (Barking), 100, 9-19
Open this publication in new window or tab >>Microstructure, mechanical and thermal oxidation behavior of AlNbTiZr high entropy alloy
2018 (English)In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 100, p. 9-19Article in journal (Refereed) Published
Abstract [en]

The developed as-cast AlNbTiZr high entropy alloy (HEA) resulted in the formation of solid solution bcc dendrites along with the inter-dendritic Zr2Al intermetallic phase. Due to low-density of 5.74 g/cm3 and high yield strength of about 1650 MPa (under compression testing), the alloy exhibited high specific yield strength of approximately 287 kPa m3/kg. Further, the AlNbTiZr HEA showed high fracture strength of 1950 MPa and substantial plastic strain of approximately 17.9%. During the isothermal thermo-gravimetry analysis in the synthetic air, at 873, 973, 1073, 1173 and 1273 K for 3 h, the mass gain behavior of the alloy was nearly parabolic indicating the formation of the protective oxide layer. Further, the long-term oxidation studies of the AlNbTiZr HEA carried out in open air atmosphere for 50 h at 873, 1073 and 1273 K confirmed that the oxide layers formed were protective, intact, and spallation did not occur. Formation of complex oxides such as AlNbO4 and Ti2ZrO6 along with Al2O3, NbO, ZrO2, and TiO2 as confirmed by X-ray diffraction could have led to the sluggish oxidation kinetics of the AlNbTiZr HEA. In contrast, the HfNbTiZr HEA showed poor oxidation resistance at 873 K.

Keywords
High entropy alloys, Oxidation, Mechanical, Casting, Microstructure, Scanning electron microscopy
National Category
Materials Engineering
Identifiers
urn:nbn:se:du-31406 (URN)10.1016/j.intermet.2018.05.015 (DOI)
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-9436-4862

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