scholarly journals Solute hydrogen and hydride phase implications on the plasticity of zirconium and titanium alloys: a review and some recent advances

2017 ◽  
Vol 375 (2098) ◽  
pp. 20160417 ◽  
Author(s):  
E. Conforto ◽  
I. Guillot ◽  
X. Feaugas
Keyword(s):  
Prismatic Slip ◽  
Misfit Dislocations ◽  
Orientation Relationships ◽  
Compact Structure ◽  
Hardening Process ◽  
Pyramidal Slip ◽  
Recent Advances ◽  
The Impact ◽  
Thermal Stability Of ◽  
Hydride Phases

In this contribution, we propose a review of the possible implications of hydrogen on mechanical behaviour of Zr and Ti alloys with emphasis on the mechanisms of plasticity and strain hardening. Recent advances on the impact of oxygen and hydrogen on the activation volume show that oxygen content hinders creep but hydrogen partially screens this effect. Both aspects are discussed in terms of a locking–unlocking model of the screw dislocation mobility in prismatic slip. Additionally, possible extension of this behaviour is suggested for the pyramidal slip. The low hydrogen solubility in both Zr and Ti leads in many cases to hydride precipitation. The nature of these phases depends on the hydrogen content and can show crystallographic orientation relationships with the hexagonal compact structure of the alloys. Some advances on the thermal stability of these phases are illustrated and discussed in relation with the deepening of the misfit dislocations. Under tensile loading, we showed that hydrides enhance the hardening process in relation with internal stress due to strain incompatibilities between the Zr and Ti matrix and hydride phases. Different plastic yielding processes of hydrides were identified, which progressively reduce these strain incompatibilities. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

Transmission Electron Microscopy of Shock-Deformed Sapphire

1991 ◽  
Vol 49 ◽  
pp. 966-967
Author(s):  
S.-J. Chen
Keyword(s):  
Basal Slip ◽  
Peak Pressure ◽  
Ceramic Materials ◽  
Prismatic Slip ◽  
Slip Systems ◽  
Microstructural Characteristics ◽  
Pyramidal Slip ◽  
Transmission Electron ◽  
Show Evidence ◽  
The Impact

An understanding of the micromechanisms which occur during the shock deformation of hard ceramic materials would be helpful to the development and optimization of these materials in ballistic environments. Previous studies of shock loaded alumina show evidence of plastic flow by basal slip 1/3<110> (0001), basal twinning, pyramidal slip 1/3<010>{113} and prismatic slip 1/3<101>(110), It has also been observed that the grain boundary and interphase material (e. g. glass) play an important role in determining the microstructural characteristics. In order to elucidate the response of different slip systems, as a function of the impact orientation and the magnitude of peak pressure, some experiments with single crystal alumina (sapphire) have been carried out and the preliminary results are presented here.

scholarly journals A Review of Hydride Precipitates in Titanium and Zirconium Alloys: Precipitation, Dissolution and Crystallographic Orientation Relationships

2020 ◽  
Vol 321 ◽  
pp. 11042
Author(s):  
Egle CONFORTO ◽  
Xavier FEAUGAS
Keyword(s):  
Zirconium Alloys ◽  
Zirconium Hydride ◽  
Misfit Dislocations ◽  
Orientation Relationships ◽  
Ti Alloys ◽  
Local Plastic Strain ◽  
Bulk Scale ◽  
Hydride Phases ◽  
Zr Alloys

This work proposes a review of recent results on the formation and dissolution of hydrides in HCP alloys (Ti and Zr alloys) correlated to the nature of crystallographic hydride phases and their ORs. The crystallographic coherence observed between the surface hydride layer and the substrate is very important for many applications as for biomaterials devices. Five particular orientation relationships (OR) were identified between titanium/zirconium hydride precipitates and the oc-Ti and a-Zr substrates. In addition, the nature of hydrides have a large implication on the ductility, the strain hardening, and the local plastic strain accommodation in the Ti alloys. Our studies using XDR, TEM and SEM-EBSD have been demonstrating that the nature of the hydride phase precipitates depends on the hydrogen content. DSC has been used to obtain the hydride dissolution and precipitation energy values at the bulk scale, whose difference can be associated to misfit dislocations. Local in-situ TEM dissolution observations show the depinning of part of misfit dislocations during dissolution process. Hydride reprecipitation is thus possible only if hydrogen is not driven away during heating by misfit dislocations depinning.

Use of 2½ D imaging in analysis of NiTi martensite

1978 ◽  
Vol 36 (1) ◽  
pp. 610-611
Author(s):  
G. M. Michal
Keyword(s):  
Memory Effect ◽  
Monoclinic Phase ◽  
Reaction Path ◽  
Structural Characteristics ◽  
Salient Feature ◽  
Martensite Phase ◽  
Orientation Relationships ◽  
Low Symmetry ◽  
Hydride Phases ◽  
Unusual Shape

Several TEM investigations have attempted to correlate the structural characteristics to the unusual shape memory effect in NiTi, the consensus being the essence of the memory effect is ostensible manifest in the structure of NiTi transforming martensitic- ally from a B2 ordered lattice to a low temperature monoclinic phase. Commensurate with the low symmetry of the martensite phase, many variants may form from the B2 lattice explaining the very complex transformed microstructure. The microstructure may also be complicated by the enhanced formation of oxide or hydride phases and precipitation of intermetallic compounds by electron beam exposure. Variants are typically found in selfaccommodation groups with members of a group internally twinned and the twins themselves are often observed to be internally twinned. Often the most salient feature of a group of variants is their close clustering around a given orientation. Analysis of such orientation relationships may be a key to determining the nature of the reaction path that gives the transformation its apparently perfect reversibility.

The Influence of Disintegration of Hard Coal Varieties of Different Metamorphism Grade on the Amount of Sorbed Ethane / Wpływ rozdrobnienia odmian węgla kamiennego o różnym stopniu metamorfizmu na ilości sorbowanego etanu

2013 ◽  
Vol 58 (2) ◽  
pp. 449-463 ◽  
Author(s):  
Mieczysław Żyła ◽  
Agnieszka Dudzińska ◽  
Janusz Cygankiewicz
Keyword(s):  
Sorption Isotherms ◽  
Electron Donors ◽  
Hard Coal ◽  
Coal Surface ◽  
Compact Layer ◽  
Compact Structure ◽  
Small Surface ◽  
Mining Works ◽  
The Impact ◽  
Content Of Oxygen

Ethane constitutes an explosive gas. It most often accompanies methane realizing during exploitation and mining works. In this paper the results of ethane sorption have been discussed on three grain classes of six selected hard coal samples collected from active Polish coalmines. On the basis of obtained results, it has been stated that the tested hard coals prove differentiated sorption power with reference to ethane. Te extreme amount of ethane is sorbed by low carbonized hard coal from “Jaworzno” coalmine. This sort of coal shows great porosity, and great content of oxygen and moisture. The least amount of ethane is sorbed by hard coal from “Sośnica” coalmine. This sort of coal possesses relatively a great deal of ash contents. Together with the process of coal disintegration, the amount of sorbed ethane increases for all tested coal samples. Between tested coals there are three medium carbonized samples collected from “Pniówek”, “Chwałowice” “Zofiówka” coalmines which are characterized by small surface values counted according to model BET from nitrogen sorption isotherms determined at the temperature of 77.5 K. The samples of these three coals prove the highest, from between tested coals, increase of ethane sorption occurring together with their disintegration. These samples disintegrated to 0,063-0,075 mm grain class sorb ethane in the amount corresponding with the sorption quantity of low carbonized coal from “Jaworzno” coalmine in 0.5-0.7 mm grain class. It should be marked that the low carbonized samples collected from “Jaworzno” and Wesoła” coalmines possess large specific surface and great porosity and belong to coal group of “loose” spatial structure. Regarding profusion of sorbed ethane on disintegrated medium carbonized samples from “Pniówek”, “Zofiówka”, “Chwałowice” coalmines it can be supposed that in the process of coal disintegration, breaking their “compact’ structure occurs. Loosened structure of medium carbonized coals results in increasing accessibility of ethane particles to sorption centres both electron donors and electron acceptors which are present on hard coal surface. The surface sorption centre increase may result in formation a compact layer of ethane particles on coal surface. In the formed layer, not only the strengths of vertical binding of ethane particles with the coal surface appear but also the impact of horizontal strengths appears which forms a compact layer of sorbed ethane particles. The surface layer of ethane particles may lead to explosion.

Evaluation of the Impact of Fatty Acid Methyl Ester (FAME) Contamination on the Thermal Stability of Jet A

2013 ◽  
Author(s):  
Jr Morris ◽  
Shardo Robert W. ◽  
Higgins James ◽  
Cook Kim ◽  
Tanner Rhonda ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Fatty Acid ◽  
Methyl Ester ◽  
Fatty Acid Methyl Ester ◽  
Acid Methyl Ester ◽  
Acid Methyl ◽  
The Impact ◽  
Thermal Stability Of

scholarly journals A Comprehensive Review of Winding Short Circuit Fault and Irreversible Demagnetization Fault Detection in PM Type Machines

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3309 ◽  
Author(s):  
Zia Ullah ◽  
Jin Hur
Keyword(s):  
Fault Diagnosis ◽  
Early Stage ◽  
Short Circuit ◽  
Industrial Applications ◽  
Operational Environment ◽  
Compact Structure ◽  
Torque Density ◽  
Prime Concern ◽  
Attractive Option ◽  
The Impact

Contemporary research has shown impetus in the diagnostics of permanent magnet (PM) type machines. The manufacturers are now more interested in building diagnostics features in the control algorithms of machines to make them more salable and reliable. A compact structure, exclusive high-power density, high torque density, and efficiency make the PM machine an attractive option to use in industrial applications. The impact of a harsh operational environment most often leads to faults in PM machines. The diagnosis and nipping of such faults at an early stage have appeared as the prime concern of manufacturers and end users. This paper reviews the recent advances in fault diagnosis techniques of the two most frequently occurring faults, namely inter-turn short fault (ITSF) and irreversible demagnetization fault (IDF). ITSF is associated with a short circuit in stator winding turns in the same phase of the machine, while IDF is associated with the weakening strength of the PM in the rotor. A detailed literature review of different categories of fault indexes and their strengths and weaknesses is presented. The research trends in the fault diagnosis and the shortcomings of available literature are discussed. Moreover, potential research directions and techniques applicable for possible solutions are also extensively suggested.

scholarly journals Preparation and Characterization of Spherical Submicron CL-20 by Siphon Spray Refinement

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Jiangtao Xing ◽  
Weili Wang ◽  
Wenzheng Xu ◽  
Tianle Yao ◽  
Jun Dong ◽  
...  
Keyword(s):  
Impact Sensitivity ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Crystal Forms ◽  
Refined Method ◽  
Diffraction Angle ◽  
Ultrasonic Assisted ◽  
The Impact ◽  
Thermal Stability Of

In order to improve the safety of hexanitrohexaazaisowurtzitane (CL-20), submicron CL-20 particles were prepared by a siphon ultrasonic-assisted spray refining experimental device. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), and the impact sensitivity of the samples was tested. The results show that the particle size of siphon-refined CL-20 is about 800 nm~1 μm, which is more smooth, mellow, and dense than that of CL-20 prepared by a traditional pressure-refined method. The peak diffraction angle of pressure- and siphon-refined CL-20 is basically the same as that of raw CL-20, and their crystal forms are ε type. The peak strength of pressure- and siphon-refined CL-20 decreased obviously. The apparent activation energy of pressure-refined CL-20 and siphon-refined CL-20 is 13.3 kJ/mol and 11.95 kJ/mol higher than that of raw CL-20, respectively. The thermal stability of CL-20 is improved. The activation enthalpy (ΔH#) is significantly higher than that of raw CL-20, and the characteristic drop is 70.4% and 82.7% higher than that of raw CL-20. The impact sensitivity of siphon-refined CL-20 is lower than that of pressure-refined CL-20, so the safety performance of an explosive is improved obviously.

The Optimizing of the Superficial Cold-Burst Hardening Process of the Inner Cylindrical Metallic Surfaces by Knocking with Centrifuged Balls

2000 ◽  
Author(s):  
D. Bulancea ◽  
V. Bulancea ◽  
I. Alexandru ◽  
D. Condurache
Keyword(s):  
Mechanical Characteristics ◽  
Vickers Microhardness ◽  
Rotation Speed ◽  
Correct Choice ◽  
Cylindrical Symmetry ◽  
Cold Hardening ◽  
Metallic Surfaces ◽  
Hardening Process ◽  
Processing Regimes ◽  
The Impact

Abstract The metallic interior surfaces with cylindrical symmetry have been processed by knocking them with centrifuged balls. The first author has designed the used processing tool and it has been carried out under his instructions. There have been processed cast iron and carbon steel samples, using 80 different combinations for the process parameters: axial advance S, tangential rotation speed of the processed piece V, and the impact force F between the balls and the processed surface. Using the measured values of roughness Ra, Vickers microhardness HV and of the depths of cold-hardening h, we have achieved and used an optimizing computer program for the qualitative parameters of the cold-hardening process, i.e. Ra, HV and h. Also, we found optimal solutions for the processing regime. The study establishes the ability to increase the mechanical characteristics of the turned out metallic surfaces, thus taking out any further mechanical, thermal and/or chemical superficial processing. The results of the current study allow a correct choice of the processing regimes for different materials with similar bulk properties.

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