scholarly journals Oxidation Behavior of Refractory AlNbTiVZr0.25 High-Entropy Alloy

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2526 ◽  
Author(s):  
Nikita Yurchenko ◽  
Evgeniya Panina ◽  
Sergey Zherebtsov ◽  
Gennady Salishchev ◽  
Nikita Stepanov
Keyword(s):  
Oxidation Kinetics ◽  
Oxidation Behavior ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
Breakaway Oxidation ◽  
High Entropy ◽  
Second Stage ◽  
Entire Duration ◽  
Different Temperatures ◽  
Oxidation Mechanisms

Oxidation behavior of a refractory AlNbTiVZr0.25 high-entropy alloy at 600–900 °C was investigated. At 600–700 °C, two-stage oxidation kinetics was found: Nearly parabolic oxidation (n = 0.46–0.48) at the first stage, transitioned to breakaway oxidation (n = 0.75–0.72) at the second stage. At 800 °C, the oxidation kinetics was nearly linear (n = 0.92) throughout the entire duration of testing. At 900 °C, the specimen disintegrated after 50 h of testing. The specific mass gains were estimated to be 7.2, 38.1, and 107.5, and 225.5 mg/cm2 at 600, 700, and 800 °C for 100 h, and 900 °C for 50 h, respectively. Phase compositions and morphology of the oxide scales were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was shown that the surface layer at 600 °C consisted of the V2O5, VO2, TiO2, Nb2O5, and TiNb2O7 oxides. Meanwhile, the scale at 900 °C comprised of complex TiNb2O7, AlNbO4, and Nb2Zr6O17 oxides. The oxidation mechanisms operating at different temperatures were discussed and a comparison of oxidation characteristics with the other alloys was conducted.

scholarly journals A Study of Thin Film Resistors Prepared Using Ni-Cr-Si-Al-Ta High Entropy Alloy

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Ruei-Cheng Lin ◽  
Tai-Kuang Lee ◽  
Der-Ho Wu ◽  
Ying-Chieh Lee
Keyword(s):  
Annealing Temperature ◽  
Phase Evolution ◽  
Amorphous Structure ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
Temperature Coefficient Of Resistance ◽  
X Ray ◽  
High Entropy ◽  
Transmission Electron ◽  
Thin Film Resistors

Ni-Cr-Si-Al-Ta resistive thin films were prepared on glass and Al2O3substrates by DC magnetron cosputtering from targets of Ni0.35-Cr0.25-Si0.2-Al0.2casting alloy and Ta metal. Electrical properties and microstructures of Ni-Cr-Si-Al-Ta films under different sputtering powers and annealing temperatures were investigated. The phase evolution, microstructure, and composition of Ni-Cr-Si-Al-Ta films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). When the annealing temperature was set to 300°C, the Ni-Cr-Si-Al-Ta films with an amorphous structure were observed. When the annealing temperature was at 500°C, the Ni-Cr-Si-Al-Ta films crystallized into Al0.9Ni4.22, Cr2Ta, and Ta5Si3phases. The Ni-Cr-Si-Al-Ta films deposited at 100 W and annealed at 300°C which exhibited the higher resistivity 2215 μΩ-cm with −10 ppm/°C of temperature coefficient of resistance (TCR).

Wear behavior of HVOF-sprayed Al0.6TiCrFeCoNi high entropy alloy coatings at different temperatures

2019 ◽  
Vol 358 ◽  
pp. 215-222 ◽  
Author(s):  
Lijia Chen ◽  
Kirsten Bobzin ◽  
Zheng Zhou ◽  
Lidong Zhao ◽  
Mehmet Öte ◽  
...  
Keyword(s):  
Wear Behavior ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Different Temperatures

Oxidation Behavior of NiAl Produced by Gel Combustion Synthesis

2016 ◽  
Vol 701 ◽  
pp. 122-126
Author(s):  
Tammy Anne Gonsalvez ◽  
Abreeza Manap ◽  
Nurfanizan Afandi ◽  
Halina Misran
Keyword(s):  
Combustion Synthesis ◽  
Oxidation Behavior ◽  
Mixed Oxides ◽  
Synthesis Method ◽  
Mass Gain ◽  
Isothermal Oxidation ◽  
X Ray Diffraction ◽  
Gel Combustion ◽  
Before And After ◽  
Different Temperatures

This paper presents the results of a study of the oxidation behavior of NiAl produced by gel combustion synthesis calcined at two different temperatures. The objective is to compare the oxide growth rates, oxide scale composition, morphology and elemental composition of the sample powder subjected to isothermal oxidation and calcined at 1050 °C and 1300 °C for 1, 2, 4 and 10 hours by means of mass gain measurements, X-ray diffraction (XRD), field emission scanning electron microsocopy (FESEM) and energy-dispersive spectrometry (EDX) in order to investigate the reliability of the gel combustion synthesis method and evaluate the effect of calcination temperature on the oxidation behaviour of the powder. It was found that for the sample calcined at 1300°C the sample was made up mainly of metastable and stable alumina before oxidation and stable alpha alumina after oxidation whereas for the powder calcined at 1050°C the sample was mainly composed of detrimental mixed oxides before and after oxidation. Overall findings indicate that the oxidation behavior of the powder calcined at 1300°C is more protective compared to the powder calcined at 1050°C.

scholarly journals Design and Production of a New FeCoNiCrAlCu High-Entropy Alloy: Influence of Powder Production Method on Sintering

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4342
Author(s):  
Eduardo Reverte ◽  
Monique Calvo-Dahlborg ◽  
Ulf Dahlborg ◽  
Monica Campos ◽  
Paula Alvaredo ◽  
...  
Keyword(s):  
Atomic Radius ◽  
Production Method ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
High Entropy ◽  
Powder Production ◽  
Production Techniques ◽  
Fcc Phase ◽  
Domain Iii

The structure of FeCoNiCrAl1.8Cu0.5 high-entropy alloys (HEA) obtained by two different routes has been studied. The selection of the composition has followed the Hume–Rothery approach in terms of number of itinerant electrons (e/a) and average atomic radius to control the formation of specific phases. The alloys were obtained either from a mixture of elemental powders or from gas-atomised powders, being consolidated in both cases by uniaxial pressing and vacuum sintering at temperatures of 1200 °C and 1300 °C. The characterization performed in the sintered samples from both types of powder includes scanning electron microscopy, X-ray diffraction, differential thermal analysis, and density measurements. It was found that the powder production techniques give similar phases content. However, the sintering at 1300 °C destroys the achieved phase stability of the samples. The phases identified by all techniques and confirmed by Thermo-Calc calculations are the following: a major Co-Ni-Al-rich (P1) BCC phase, which stays stable after 1300 °C sintering and homogenising TT treatments; a complex Cr-Fe-rich (P2) B2 type phase, which transforms into a sigma phase after the 1300 °C sintering and homogenising TT treatments; and a very minor Al-Cu-rich (P3) FCC phase, which also transforms into Domain II and Domain III phases during the heating at 1300 °C and homogenising TT treatments.

scholarly journals Elastic, Mechanical and Thermophysical properties of Single-Phase Quaternary ScTiZrHf High-Entropy Alloy

2021 ◽  
Vol 22 (4) ◽  
pp. 687-696
Author(s):  
Sachin Rai ◽  
Navin Chaurasiya ◽  
Pramod K. Yadawa
Keyword(s):  
Mechanical Properties ◽  
Elastic Constants ◽  
Room Temperature ◽  
Single Phase ◽  
Mechanical Characterization ◽  
Ultrasonic Attenuation ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Different Temperatures ◽  
Ultrasonic Parameters

Consequent to the interaction potential model, the high-order elastic constants at high entropy alloys in single-phase quaternary ScTiZrHf have been calculated at different temperatures. Elastic constants of second order (SOECs) helps to determine other ultrasonic parameters. With the help of SOECs other elastic moduli, bulk modulus, shear modulus, Young’s modulus, Pugh’s ratio, elastic stiffness constants and Poisson’s ratio are estimated at room temperature for elastic and mechanical characterization. The other ultrasonic parameters are calculated at room temperature for elastic and mechanical characterization. The temperature variation of ultrasonic velocities along the crystal's z-axis is evaluated using SOECs. The temperature variation of the  average debye velocity and the thermal relaxation time (τ) are also estimated along this orientation axis. The ultrasonic properties correlated with elastic, thermal and mechanical properties which is temperature dependent is also discussed. The ultrasonic attenuation due to phonon – phonon (p-p) interactions is also calculated at different temperatures. In the study of ultrasonic attenuation such as a function of temperature, thermal conductivity appears to be main contributor and p- p interactions are the responsible reason of attenuation and found that the mechanical properties of the high entropy alloy ScTiZrHf are superior at room temperature.

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