Microstructural Development and Phase Changes in Reaction Bonded Boron Carbide

This paper reports the microstructural evolution and mechanical properties of a low-density Al0.3NbTa0.8Ti1.5V0.2Zr refractory high-entropy alloy (RHEA) prepared by means of a combination of mechanical alloying and spark plasma sintering (SPS). Prior to sintering, the morphology, chemical homogeneity and crystal structures of the powders were thoroughly investigated by varying the milling times to find optimal conditions for densification. The sintered bulk RHEAs were produced with diverse feedstock powder conditions. The microstructural development of the materials was analyzed in terms of phase composition and constitution, chemical homogeneity, and crystallographic properties. Hardness and elastic constants also were measured. The calculation of phase diagrams (CALPHAD) was performed to predict the phase changes in the alloy, and the results were compared with the experiments. Milling time seems to play a significant role in the contamination level of the sintered materials. Even though a protective atmosphere was used in the entire manufacturing process, carbide formation was detected in the sintered bulks as early as after 3 h of powder milling. Oxides were observed after 30 h due to wear of the high-carbon steel milling media and SPS consolidation. Ten hours of milling seems sufficient for achieving an optimal equilibrium between microstructural homogeneity and refinement, high hardness and minimal contamination.

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The Interpretation of Crystal Lattice Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009600x ◽

1972 ◽

Vol 30 ◽

pp. 550-551

Author(s):

J. M. Cowley ◽

Sumio Iijima

Keyword(s):

Crystal Orientation ◽

Diffraction Theory ◽

Phase Changes ◽

Electron Wave ◽

Crystal Lattices ◽

Heavy Atoms ◽

Lattice Images ◽

The Right ◽

Intuitive Interpretation ◽

Suitable Approximation

The imaging of detailed structures of crystal lattices with 3 to 4Å resolution, given the correct conditions of microscope defocus and crystal orientation and thickness, has been used by Iijima (this conference) for the study of new types of crystal structures and the defects in known structures associated with fluctuations of stoichiometry. The image intensities may be computed using n-beam dynamical diffraction theory involving several hundred beams (Fejes, this conference). However it is still important to have a suitable approximation to provide an immediate rough estimate of contrast and an evaluation of the intuitive interpretation in terms of an amplitude object.For crystals 100 to 150Å thick containing moderately heavy atoms the phase changes of the electron wave vary by about 10 radians suggesting that the “optimum defocus” theory of amplitude contrast for thin phase objects due to Scherzer and others can not apply, although it does predict the right defocus for optimum imaging.

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Microstructural Development in Nb-Ti Multifilamentary Superconductors During Processing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117911 ◽

1985 ◽

Vol 43 ◽

pp. 190-191

Author(s):

A. W. West

Keyword(s):

Heat Treatment ◽

Critical Current Density ◽

Copper Matrix ◽

Wire Drawing ◽

Heat Treatments ◽

Microstructural Development ◽

Final Size ◽

Density Values ◽

The Wire ◽

Multifilamentary Superconductors

The influence of the filament microstructure on the critical current density values, Jc, of Nb-Ti multifilamentary superconducting composites has been well documented. However the development of these microstructures during composite processing is still under investigation.During manufacture, the multifilamentary composite is given several heat treatments interspersed in the wire-drawing schedule. Typically, these heat treatments are for 5 to 80 hours at temperatures between 523 and 573K. A short heat treatment of approximately 3 hours at 573K is usually given to the wire at final size. Originally this heat treatment was given to soften the copper matrix, but recent work has shown that it can markedly change both the Jc value and microstructure of the composite.

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Processing and characterization of YBa2Cu3O7−x/Ag composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173364 ◽

1990 ◽

Vol 48 (4) ◽

pp. 46-47

Author(s):

Jafar Javadpour ◽

Bradley L. Thiel ◽

Sarikaya Mehmet ◽

Ilhan A. Aksay

Keyword(s):

Composite System ◽

Precursor Solution ◽

Microstructural Development ◽

Superconducting Properties ◽

Practical Applications ◽

Nitrate Precursor ◽

Cold Pressed ◽

Tape Cast ◽

Composite Samples

Practical applications of bulk YBa2Cu3O7−x materials have been limited because of their inadequate critical current density (jc) and poor mechanical properties. Several recent reports have indicated that the addition of Ag to the YBa2Cu3O7−x system is beneficial in improving both mechanical and superconducting properties. However, detailed studies concerning the effect of Ag on the microstructural development of the cermet system have been lacking. Here, we present some observations on the microstructural evolution in the YBa2Cu3O7−x/Ag composite system.The composite samples were prepared by mixing various amounts (2.5 - 50 wt%) AgNO3 in the YBa2Cu3O7−x nitrate precursor solution. These solutions were then spray dried and the resulting powders were either cold pressed or tape cast. The microstructures of the sintered samples were analyzed using SEM (Philips 515) and an analytical TEM (Philips 430T).The SEM micrographs of the compacts with 2.5 and 50 wt% Ag addition sintered at 915°C (below the melting point of Ag) for 1 h in air are displayed in Figs. 1 and 2, respectively.

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Gravitational effects on microstructural development in liquid phase sintered alloys

Metal Powder Report ◽

10.1016/s0026-0657(97)84687-5 ◽

1997 ◽

Vol 53 (7-8) ◽

pp. 39

Author(s):

T Courtney

Keyword(s):

Liquid Phase ◽

Microstructural Development ◽

Gravitational Effects ◽

Sintered Alloys

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Dynamic X-ray imaging of the penetration of boron carbide

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2000997 ◽

2000 ◽

Vol 10 (PR9) ◽

pp. Pr9-583-Pr9-588 ◽

Cited By ~ 4

Author(s):

W. A. Gooch ◽

M. S. Burkins ◽

G. Hauver ◽

P. Netherwood ◽

R. Benck

Keyword(s):

Boron Carbide ◽

X Ray ◽

X Ray Imaging

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Remote diagnostics of vibrations of dynamic objects by Doppler microwave sensors

Metrologiya ◽

10.32446/0132-4713.2020-3-25-42 ◽

2020 ◽

pp. 25-42

Author(s):

Dmitrii V. Khablov

Keyword(s):

Intelligent Systems ◽

Electromagnetic Waves ◽

Continuous Monitoring ◽

Phase Changes ◽

Vibration Diagnostics ◽

Remote Diagnostics ◽

Active Vibration ◽

Dynamic Objects ◽

Microwave Sensors ◽

Non Destructive

This paper describes a promising method for non-contact vibration diagnostics based on the use of Doppler microwave sensors. In this case, active irradiation of the object with electromagnetic waves and the allocation of phase changes using two-channel quadrature processing of the received reflected signal are used. The modes of further fine analysis of the resulting signal using spectral or wavelet transformations depending on the nature of the active vibration are considered. The advantages of this non-contact and remote vibration analysis method for the study of complex dynamic objects are described. The convenience of the method for machine learning and use in intelligent systems of non-destructive continuous monitoring of the state of these objects by vibration is noted.

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