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1. Effect of microstructure on Ti3Al precipitation during ageing of Ti-6Al-4V alloy

Author

Callegari B., Marçola J. V., Aristizabal K., Soldera F. A., Mücklich F., and Pinto H. C.

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

The aim of the present work is to explore the age-hardening potential of Ti-6Al-4V (Ti-64) alloy with variation of the starting microstructure, with attention to the precipitation of nano-sized Ti3Al phase, as influenced by microstructural features. The alloy was either solution-treated or deformed by compression at temperatures above and below its β-transus to produce microstructures comprising martensitic, lamellar and globular α morphologies, as well as the existence or absence of β phase, and subsequently submitted to ageing treatments at 400°C/8h using in situ x-ray diffraction. Precipitated fractions of Ti3Al were obtained via Rietveld refinement and aged microstructures were characterized by micro-hardness measurements. Results show that α2 precipitation is favored by a globular morphology of α and hindered by a martensitic α morphology, and suggest that the presence of β phase also has as influence on precipitation.

Published
2020
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27. Characterization of As-Welded Microstructure in a P91 Steel.

Author

MARZOCCA, A. L., SOLDERA, F., ZALAZAR, M., DANÓN, C. A., and LUPPO, M. I.

Subjects
MICROHARDNESS, ELECTRIC welding, TRANSMISSION electron microscopy, SCANNING electron microscopy, STEEL, MICROSTRUCTURE
Abstract

The microstructure of the heat affected zone (HAZ) and fusion zone (FZ) in the as-welded condition of a single-pass weld performed by the flux-cored arc welding (FCAW) process was studied in a P91 steel using microhardness measurements, field-emission scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The evolution of precipitates in each region of the single-pass weld was analyzed, and particular attention was paid to the presence of retained austenite (RA). Experimental observations indicated that M23C6 carbide played a major role in the thermal cycle associated with the weldment. On one hand, the dissolution of M23C6 led to the precipitation of spherical NbCN in the fine-grained HAZ (FGHAZ) near the coarse-grained HAZ (CGHAZ). On the other hand, the total or partial dissolution of M23C6 carbides changed the chemical composition of the initially formed austenite. In the regions where the M23C6 carbides were completely dissolved (i.e., the CGHAZ and FZ), retained austenite was observed as a thin, continuous film along primary austenite grains and lath boundaries. Instead, a shell of retained austenite was observed around some partially dissolved M23C6 of the intercritical HAZ (ICHAZ) and FGHAZ. [ABSTRACT FROM AUTHOR]

Published
2024
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34. Room temperature self-assembled growth of vertically aligned columnar copper oxide nanocomposite thin films on unmatched substrates

Author

Wang, Y., Ghanbaja, J., Bruyère, S., Soldera, F., Horwat, D., Mücklich, F., and Pierson, J. F.

Subjects
lcsh:R, lcsh:Medicine, lcsh:Q, lcsh:Science, Article
Abstract

In this work, we report the self-assembled growth of vertically aligned columnar Cu2O + Cu4O3 nanocomposite thin films on glass and silicon substrates by reactive sputtering at room temperature. Microstructure analyses show that each phase in nanocomposite films has the columnar growth along the whole thickness, while each column exhibits the single phase characteristics. The local epitaxial growth behavior of Cu2O is thought to be responsible for such an unusual microstructure. The intermediate oxygen flow rate between those required to synthesize single phase Cu2O and Cu4O3 films produces some Cu2O nuclei, and then the local epitaxial growth provides a strong driving force to promote Cu2O nuclei to grow sequentially, giving rise to Cu2O columns along the whole thickness. Lower resistivity has been observed in such kind of nanocomposite thin films than that in single phase thin films, which may be due to the interface coupling between Cu2O and Cu4O3 columns.

Published
2017
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43. Quantitative investigation of material erosion caused by high-pressure discharges in air and nitrogen

Author

Lasagni, A., Soldera, F., and Mücklich, F.

Abstract

Single-spark erosion experiments were conducted in different pure metal samples. The samples were used as the cathode, and a platinum electrode was used as the anode. The sparks were produced at high pressure and room temperature, having at this conditions a breakdown phase (ca. 100 ns) and an arc phase (several hundreds of μs). The crater volumes on the different materials were correlated with several properties of materials, in view of different models of material erosion related to melting enthalpy, vaporization enthalpy and sublimation energy. It was found that the quotient between the eroded volume and the spark energy correlates well with a function of the energy necessary to heat the material up to the melting point and to melt it. The particle ejection model can be used to explain this process. Moreover, it was found that the crater shape is related to the surface tension of the molten material. These investigations may be relevant for the development of high-performance materials for electrode and contact applications.

Published
2021
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44. Features of electronic and lattice mechanisms of transboundary heat transfer in multilayer nanolaminate TiA1N/Ag coatings

Author

Kovalev, A. I., Wainstein, D. L., Vakhrushev, V. O., Gago, R., Soldera, F., Endrino, José L., Fox-Rabinovich, German S., and Veldhuis, Stephen C.

Subjects
Physics::Optics
Abstract

Plasmon resonance heterogeneities were identified and studied along Ag and TiAlN layers within a multilayer stack in nanolaminate TiAlN/Ag coatings. For this purpose, a high-resolution plasmon microscopy was used. The plasmons intensity, energy, and depth of interface plasmon-polariton penetration were studied by scanning reflected electron energy loss spectroscopy. The heat conductivity of such metal-insulator-metal (MIM) nanolaminate coatings was measured by laser reflectometry. Dependencies of thermal conductivity coefficient of coatings, MIM interfaces, and resistivity of Ag layers as a function of the Ag-TiAlN bilayer thickness were calculated on the basis of experimental data. The contribution of plasmon resonance confinement to the abnormal lower thermal conductivity in the MIM metamaterial with Ag layer thickness below 25 nm is discussed. In particular, the results highlight the relevant role of different heat transfer mechanisms between MI and IM interfaces: asymmetry of plasmon-polariton interactions on upper and lower boundaries of Ag layer and asymmetry of LA and TA phonons propagation through interfaces.

Published
2017

45. Oxide Layer Evolution of Cast Fe24Cr12NiXNb Heat-Resistant Cast Steels at 900°C in Atmospheric Air.

Author

Ramos, P. A., Coelho, R. S., Pinto, H. C., Soldera, F., Mücklich, F., and Brito, P. P.

Subjects
CAST steel, STAINLESS steel, STEEL founding, NICKEL-chromium alloys, AUSTENITIC stainless steel, ENERGY dispersive X-ray spectroscopy, HEAT resistant alloys, ELEMENTAL analysis
Abstract

The austenitic stainless steels are a group of alloys normally used under high mechanical and thermal requests, in which high temperature oxidation is normally present due to oxygen presence. This study examines the oxide layer evolution for Fe24Cr12NiXNb modified austenitic stainless steel A297 HH with 0,09%Nb and 0,77%Nb content at 900°C under atmospheric air and isothermal oxidation. The modifiers elements such as Mo, Co and Ti, added to provide high mechanical strength, varied due to the casting procedure, however main elements such as Cr, Ni, Mn and Si were kept at balanced levels to avoid microstructure changing. The oxide layer analysis was performed by confocal laser scanning microscopy (CLS) and scanning electron microscopy (SEM). The elemental analysis of the different phases was measured with energy dispersive X-ray spectroscopy (EDX). The Nb-alloyed steel generated a thicker Cr oxide layer. Generally elemental Nb did not provide any noticeable difference in oxide scale growth, for the specific range of Nb amount and temperature studied. High temperature oxidation up to 120h was characterized by protective Cr oxidation, after this period a non-protective Fe-based oxidation took place. Cr, Fe and Ni oxides were observed in the multilayer oxide scale. [ABSTRACT FROM AUTHOR]

Published
2021
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47. Electronic structures of Cu2O, Cu4O3, and CuO: A joint experimental and theoretical study

Author

Wang, Y., Lany, S., Ghanbaja, J., Fagot-Revurat, Y., Chen, Y. P., Soldera, F., Horwat, D., Mücklich, F., Pierson, J. F., Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), National Renewable Energy Laboratory (NREL), Department of Physics, Xiangtan University, Department for Materials Science, Functional Materials, and Saarland University [Saarbrücken]

Subjects
Condensed Matter::Materials Science, Condensed Matter::Strongly Correlated Electrons, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]
Abstract

International audience; A joint experimental and theoretical study is presented for the electronic structures of copper oxides including Cu2O, CuO, and the metastable mixed-valence oxide Cu 4 O 3. The optical band gap is determined by experimental optical absorption coefficient, and the electronic structure in valence and conduction bands is probed by photoemission and electron energy loss spectroscopies, respectively. The experimental results are compared with many-body GW calculations utilizing an additional on-site potential for d-orbital energies that facilitates tractable and predictive computations. The side-by-side comparison between the three oxides, including a band insulator (Cu2O) and two Mott/charge-transfer insulators (CuO, Cu4O3) leads to a consistent picture for the optical and band-structure properties of the Cu oxides, strongly supporting indirect band gaps of about 1.2 and 0.8 eV in CuO and Cu4O3 , respectively. This comparison also points towards surface oxidation and reduction effects that can complicate the interpretation of the photoemission spectra.

Published
2016
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50. Features of electronic and lattice mechanisms of transboundary heat transfer in multilayer nanolaminate TiAlN/Ag coatings

Author

Russian Science Foundation, European Commission, Comunidad de Madrid, Kovalev, A. I., Wainstein, D. L., Vakhrushev, V. O., Gago, Raúl, Soldera, F., Endrino, J. L., Fox-Rabinovich, G. S., Veldhuis, S., Russian Science Foundation, European Commission, Comunidad de Madrid, Kovalev, A. I., Wainstein, D. L., Vakhrushev, V. O., Gago, Raúl, Soldera, F., Endrino, J. L., Fox-Rabinovich, G. S., and Veldhuis, S.

Abstract

Plasmon resonance heterogeneities were identified and studied along Ag and TiAlN layers within a multilayer stack in nanolaminate TiAlN/Ag coatings. For this purpose, a high-resolution plasmon microscopy was used. The plasmons intensity, energy, and depth of interface plasmon-polariton penetration were studied by scanning reflected electron energy loss spectroscopy. The heat conductivity of such metal-insulator-metal (MIM) nanolaminate coatings was measured by laser reflectometry. Dependencies of thermal conductivity coefficient of coatings, MIM interfaces, and resistivity of Ag layers as a function of the Ag-TiAlN bilayer thickness were calculated on the basis of experimental data. The contribution of plasmon resonance confinement to the abnormal lower thermal conductivity in the MIM metamaterial with Ag layer thickness below 25 nm is discussed. In particular, the results highlight the relevant role of different heat transfer mechanisms between MI and IM interfaces: asymmetry of plasmon-polariton interactions on upper and lower boundaries of Ag layer and asymmetry of LA and TA phonons propagation through interfaces.

Published
2017

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