Felicia Tolea

Dr. Felicia Tolea

orcid

Research Focus & Metrics

Academic Career Length

12Years (2015-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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17 June 2019 in Materials
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Journal Article
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Gheorghe GurauGheorghe Gurau
Gheorghe Gurau
CGCarmela Gurau
Carmela Gurau
FTFelicia Tolea
Felicia Tolea
VSVedamanikam SAMPATH
Vedamanikam SAMPATH
Severe plastic deformation (SPD) is widely considered to be the most efficient process in obtaining ultrafine-grained bulk materials. The aim of this study is to examine the effects of the SPD process on Ni-Fe-Ga ferromagnetic shape memory alloys (FSMA). High-speed high-pressure torsion (HSHPT) was applied in the as-cast state. The exerted key parameters of deformation are described. Microstructural changes, including morphology that were the result of processing, were investigated by optical and scanning electron microscopy. Energy-dispersive X-ray spectroscopy was used to study the two-phase microstructure of the alloys. The influence of deformation on microstructural features, such as martensitic plates, intragranular γ phase precipitates, and grain boundaries’ dependence of the extent of deformation is disclosed by transmission electron microscopy. Moreover, the work brings to light the influence of deformation on the characteristics of martensitic transformation (MT). Vickers hardness measurements were carried out on disks obtained by SPD so as to correlate the hardness with the microstructure. The method represents a feasible alternative to obtain ultrafine-grained bulk Ni-Fe-Ga alloys.

17 August 2021 in Materials
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CGCarmela Gurau
Carmela Gurau
Gheorghe GurauGheorghe Gurau
Gheorghe Gurau
FTFelicia Tolea
Felicia Tolea
BPBogdan Popescu
Bogdan Popescu
MBMihaela Banu
Mihaela Banu
Leandru Gheorghe BujoreanuLeandru Gheorghe Bujoreanu
Leandru Gheorghe Bujoreanu
This work focuses on the temperature evolution of the martensitic phase ε (hexagonal close packed) induced by the severe plastic deformation via High Speed High Pressure Torsion method in Fe57Mn27Si11Cr5 (at %) alloy. The iron rich alloy crystalline structure, magnetic and transport properties were investigated on samples subjected to room temperature High Speed High Pressure Torsion incorporating 1.86 degree of deformation and also hot-compression. Thermo-resistivity as well as thermomagnetic measurements indicate an antiferromagnetic behavior with the Néel temperature (TN) around 244 K, directly related to the austenitic γ-phase. The sudden increase of the resistivity on cooling below the Néel temperature can be explained by an increased phonon-electron interaction. In-situ magnetic and electric transport measurements up to 900 K are equivalent to thermal treatments and lead to the appearance of the bcc-ferrite-like type phase, to the detriment of the ε(hcp) martensite and the γ (fcc) austenite phases.

26 May 2021 in Transactions of the Indian Institute of Metals
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Journal Article
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BPB. Popescu
B. Popescu
CGC. Gurau
C. Gurau
Gheorghe GurauGheorghe Gurau
Gheorghe Gurau
MTM. Tolea
M. Tolea
MSM. Sofronie
M. Sofronie
FTFelicia Tolea
Felicia Tolea

1 May 2017 in Solid State Communications
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Journal Article
Open access
FTFelicia Tolea
Felicia Tolea
MŢM. Ţolea
M. Ţolea
MVM. Văleanu
M. Văleanu
Shape memory alloys are known to memorise one -or several- temperatures at which the martensite-austenite transformation was stopped before completion in the past, the memory manifesting as specific dips in subsequent calorimetric scans. Previous studies have shown that this memory can be erased by heating to higher temperatures than the ones previously recorded. In this paper, we study a distinct memory fading effect which takes place by heating to a lower temperature. This effect is reported in NiFeGa as polycrystalline ribbons, the alloy being initially studied as bulk for which the thermal memory effect was not found. If, after an initial incomplete heating up to T1 one performs a second incomplete heating up to T2

2 March 2024 in Nanomaterials
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CCCristiana Diana Cirstea
Cristiana Diana Cirstea
EPErwin Povoden-Karadeniz
Erwin Povoden-Karadeniz
VCVasile Cirstea
Vasile Cirstea
FTFelicia Tolea
Felicia Tolea
EKErnst Kozeschnik
Ernst Kozeschnik
The thermodynamic and kinetic simulations based on the re-assessment of the thermodynamic and kinetic database of the Ni-Ti-Cu system were employed to predict the phenomena of mechanical alloying, spark plasma sintering and thermal properties of the intriguing Ni-Ti-Cu system. Thermodynamic calculations are presented for the stable and unstable phases of NiTiCu materials and support a correlation with the evolving microstructure during the technological process. Also, the thermal conductivity, the thermal diffusivity and the specific heat of spark plasma sintered and aged Cu-alloyed NiTi-based shape memory alloys (NiTiCu) with two compositions, Ni45Ti50Cu5 and Ni40Ti50Cu10, are evaluated and the influence of mechanical alloying and precipitates on thermal properties is discussed. Measurements of these thermal properties were carried out from 25 °C up to 175 °C using the laser flash method, as well as differential scanning calorimetry. The thermal hysteresis of the 20 mm diameter samples was between 8.8 and 24.5 °C. The observed T0 temperatures from DSC experimental transformation features are in reasonable accordance with the thermodynamic predictions. The determined k values are between 20.04 and 26.87 W/m K and in agreement with the literature results. Moreover, this paper can provide some suggestions for the preparation of NiTiCu shape memory alloys and their applications.

19 October 2022 in Nanomaterials
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MSMihaela Sofronie
Mihaela Sofronie
BPBogdan Popescu
Bogdan Popescu
MEMonica Enculescu
Monica Enculescu
MTMugurel Tolea
Mugurel Tolea
FTFelicia Tolea
Felicia Tolea
The influence of processing on the martensitic transformation and related magnetic properties of the Ni55Fe18Nd2Ga25 ferromagnetic shape memory alloy, as bulk and ribbons prepared by the melt spinning method and subjected to different thermal treatments, is investigated. Structural, calorimetric, and magnetic characterizations are performed. Thermal treatment at 1173 K induces a decrease in both the Curie and the martensitic transformation temperatures, while a treatment at 673 K produces the structural ordering of the ribbons, hence an increase in TC. A maximum value of the magnetic entropy variation of −5.41 J/kgK was recorded at 310 K for the as quenched ribbons. The evaluation of the magnetoresistive effect shows a remarkable value of −13.5% at 275 K on the bulk sample, which is much higher than in the ribbons.