Strength of Metals in the Light of Modern Physics

1936 ◽  
Vol 40 (309) ◽  
pp. 586-621 ◽  
Author(s):  
H. J. Gough ◽  
W. A. Wood
Keyword(s):  
Atomic Structure ◽  
Internal Stresses ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Modern Physics ◽  
Correct Understanding ◽  
Development Methods ◽  
First Time ◽  
The Relationship

SummaryThe strengths of the metals at present available to industry are of especial importance to the aeronautical engineer who is also in a position to appreciate the need for greatly improved materials, the absence of which often places restriction on much needed developments. Although the materials of the future may become available by the somewhat fortuitous development methods at present employed, it is undeniable that greatly accelerated developments would result if a correct understanding was obtained of the fundamental characteristics of the cohesion and fracture of metals, of which the former belongs to the field of the atomic physicist.It has been found possible, for the first time, to show that failure under static and fatigue stressing is associated with changes in the crystalline structure which are identical. These changes are (1) a dislocation of the initially perfect grains into large components which vary in orientation from that of the internal grain by amounts up to about 2°,(2) the formation of “crystallites,” approximately 10-4 to 10-5 cm. in size, whose orientation varies widely from that of the original grains, and (3) the presence of severe internal stresses in the crystallites. At fracture, whatever the type of applied stressing, the whole of the specimen behaves to the X-ray beam as a medium of crystallites showing marked lattice distortion and oriented completely at random. X-ray diffraction methods are shown to distinguish clearly between the effects of the application of safe and unsafe ranges of stress; the first method that has been successful in this respect.In order to show the relationship between the new work described and previous work dealing with the use of X-rays in studying the deformation characteristics of metals, a preliminary section of the paper deals with cold-rolling and drawing. A survey is also presented of the present position regarding strength and atomic structure, together with references to various theories regarding the imperfections of crystals as encountered in practice. An introductory section describes briefly the atomic structure of metals, as revealed by X-rays.

scholarly journals Chiral 1,2-Subnaphthalocyanines

2021 ◽  
Author(s):  
Soji Shimizu ◽  
Akito Miura ◽  
Tebello Nyokong ◽  
Samson Khene ◽  
Nagao Kobayashi
Keyword(s):  
Diffraction Analysis ◽  
Magnetic Circular Dichroism ◽  
Small Variation ◽  
Soret Band ◽  
Chiral Molecules ◽  
X Ray Diffraction ◽  
Enantiomerically Pure ◽  
X Ray ◽  
First Time ◽  
The Relationship

<p>Following the first suggestion of inherent molecular chirality in asymmetrically substituted subphthalocyanines by Torres and co-workers in 2000, elucidation of the relationship between structure and chirality has become an important issue. However, separation of the enantiomers has been prevented by the low solubility of the molecules synthesized to date, and it has not been possible to link the CD signs and intensities to their absolute structures. Recently, we observed that 1,2-subnaphthalocyanines possess two diastereomers with respect to the arrangement of the naphthalene moieties and that these novel chiral molecules exhibit moderate solubility in common organic solvents. This has enabled us to separate all of the diastereomers and enantiomers. The two diastereomers have been completely characterized by NMR spectroscopy and X-ray diffraction analysis. The absorption and magnetic circular dichroism spectra, together with theoretical calculation, reveal a small variation in the frontier molecular orbitals of the 1,2-subnaphthalocyanines compared with conventional subphthalocyanines, except for destabilization of the HOMO–3, which results in a characteristic absorption in the Soret band region. The chirality of 1,2-subnaphthalcyanines, including the CD signs and intensities, is discussed in detail for the first time with enantiomerically pure molecules whose absolute structures have been elucidated by single-crystal X-ray diffraction analysis.</p>

scholarly journals In Situ X-Ray Diffraction during Casting: Study of Hot Tearing in Al-Zn Alloys

2015 ◽  
Vol 1120-1121 ◽  
pp. 1134-1141 ◽  
Author(s):  
Jean Marie Drezet ◽  
Bastien Mireux ◽  
Guven Kurtuldu
Keyword(s):  
Volume Fraction ◽  
Solid Phase ◽  
Hot Spot ◽  
Solid Volume Fraction ◽  
Internal Stresses ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zn Alloys

During solidification of metallic alloys, coalescence corresponds to the formation of solid bridges between grains when both solid and liquid phases are percolated. As such, it represents a key transition with respect to the mechanical behaviour of solidifying alloys and to the prediction of solidification cracking. Coalescence starts at the coherency point when the grains begin to touch each other, but are unable to sustain any tensile loads. It ends up at the rigidity temperature when the solid phase is sufficiently coalesced to transmit macroscopic tensile strains and stresses. This temperature, also called mechanical or tensile coherency temperature, is a major input parameter in numerical modelling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. The rigidity temperature has been determined in Al Zn alloys using in situ X-ray diffraction (XRD) during casting in a dog bone shaped mould. This set-up allows the sample to build up internal stress naturally as its contraction is prevented. The cooling on both extremities of the mould induces a hot spot at the middle of the sample which is irradiated by X-rays. Diffraction patterns were recorded every 0.5 s using a detector covering a 426 x 426 mm2area. The change of diffraction angles allowed us to observe agglomeration/decohesion of growing grain clusters and to determine a solid volume fraction at rigidity around 98 % depending on solidification time for grain refined Al 6.2 wt% Zn alloys.

Origin of quasi-mosaic effect for symmetric skew planes in a silicon or germanium plate

2016 ◽  
Vol 49 (5) ◽  
pp. 1810-1813
Author(s):  
Valerio Bellucci ◽  
Riccardo Camattari ◽  
Gianfranco Paternò ◽  
Vincenzo Guidi ◽  
Andrea Mazzolari
Keyword(s):  
European Synchrotron Radiation Facility ◽  
X Rays ◽  
X Ray Diffraction ◽  
Particle Beams ◽  
Charged Particle Beams ◽  
Modern Physics ◽  
Silicon And Germanium ◽  
Crystallographic Planes ◽  
First Time ◽  
Good Agreement

Bent silicon and germanium crystals are used for several modern physics applications, above all for focusing of hard X-rays and for steering of charged particle beams by means of channeling and related coherent phenomena. In particular, anisotropic deformations are effectively exploited for these applications. A typical anisotropic deformation that is used is the quasi-mosaic (QM) curvature. It involves the bending of crystallographic planes that would be otherwise flat in the case of an isotropic medium. Here, the curvature the {110} planes was obtained through the quasi-mosaic effect in the symmetric configuration for the first time. This achievement is important because the {110} family of planes is highly efficient for both the applications mentioned above. Until now, the curvature of {110} planes in the QM configuration has not been used because it vanishes if the direction of the planes is aligned with the applied moment that bends the crystal plate. Indeed, to obtain the curvature of this particular family of crystallographic planes, the 〈110〉 direction has not to be aligned with respect to the imparted moment that bends the plate, i.e. the {110} planes have to be skew planes. Experimental verification of the quasi-mosaic curvature for the {110} planes was provided through hard X-ray diffraction at beamline ID15A of the European Synchrotron Radiation Facility in Grenoble, France, showing good agreement with the theoretical expectation.

Solving the iron quantification problem in low-kV EPMA: An essential step toward improved analytical spatial resolution in electron probe microanalysis—Olivines

2019 ◽  
Vol 104 (8) ◽  
pp. 1131-1142 ◽  
Author(s):  
Aurélien Moy ◽  
John H. Fournelle ◽  
Anette von der Handt
Keyword(s):  
Melt Inclusions ◽  
Accurate Solution ◽  
Electron Interaction ◽  
X Rays ◽  
Transition Elements ◽  
X Ray ◽  
Iron Quantification ◽  
Accurate Quantitative Analysis ◽  
First Time ◽  
The Relationship

AbstractThe relatively recent entry of field emission electron microprobes into the field of microanalysis provides another tool for the study of small features of interest (e.g., mineral and melt inclusions, ex-solution lamellae, grain boundary phases, high-pressure experimental charges). However, the critical limitation for accurate quantitative analysis of these submicrometer- to micrometer-sized features is the relationship between electron beam potential and electron scattering within the sample. To achieve submicrometer analytical volumes from which X-rays are generated, the beam accelerating voltage must be reduced from 15–20 to ≤10 kV (often 5 to 7 kV) to reduce the electron interaction volume from ~3 to ~0.5 μm in common geological materials. At these low voltages, critical Kα X-ray lines of transition elements such as Fe are no longer generated, so L X-ray lines must be used. However, applying the necessary matrix corrections to these L lines is complicated by bonding and chemical peak shifts for soft X-ray transitions such as those producing the FeLα X-ray line. It is therefore extremely challenging to produce accurate values for Fe concentration with this approach. Two solutions have been suggested, both with limitations. We introduce here a new, simple, and accurate solution to this problem, using the common mineral olivine as an example. We also introduce, for the first time, olivine results from a new analytical device, the Extended Range Soft X-ray Emission Spectrometer.

scholarly journals On the Thermal Interpretation of Hard X-Ray Bursts from Solar Flares

1974 ◽  
Vol 57 ◽  
pp. 395-412 ◽  
Author(s):  
John C. Brown
Keyword(s):  
Solar Flares ◽  
Thermal Conduction ◽  
Temperature Structure ◽  
X Rays ◽  
X Ray ◽  
Time Variations ◽  
Relationship Of ◽  
First Time ◽  
The Relationship ◽  
Continuous Temperature

The possible validity of thermal bremsstrahlung models of flare hard X-ray bursts is investigated quantitatively. In particular, the problem of rapid thermal conduction in ‘multi-temperature’ models is adequately examined for the first time by using a continuous temperature distribution consistent with the observed X-ray spectrum. This distribution is obtained from a general analytic solution for the temperature structure required to mimick any ‘non-thermal’ spectrum, the method being equally applicable to cosmic sources.It is concluded that the thermal interpretation might extend to X-rays of hundreds of keV, a result with important consequences for flare energetics. The relationship of such a model to observations of X-ray polarization and rapid time variations is also considered.

Microscopic View on Grain Nucleation and Growth Kinetics During Solidification of Aluminum Alloys

2004 ◽  
Vol 840 ◽  
Author(s):  
N. Iqbal ◽  
N. H. van Dijk ◽  
S. E. Offerman ◽  
M. Moret ◽  
L. Katgerman ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Grain Growth ◽  
Nucleation And Growth ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffusion Limited ◽  
Model Predictions ◽  
The Difference ◽  
First Time

ABSTRACTX-ray diffraction with hard X-rays (E = 70 keV) was used to investigate the grain nucleation and grain growth during solidification of a grain refined Al-0.3Ti-0.02B (wt.%) alloy. The investigations showed for the first time the nucleation profile during solidification and how nucleation rate increases with cooling rate. The results indicate that the nucleation process is complete for solid fraction below 30 %, irrespective of the cooling rate. This is explained in terms of the release of latent heat during solidification. The growth of individual aluminium grains during solidification is experimentally observed and compared to model predictions for the diffusion limited grain growth. The experimental results are only in agreement with the theory in the first stage of the transformation. The difference between the experiment and the theory is discussed qualitatively.

scholarly journals Ionic transport and atomic structure of AgI-HgS-GeS2 glasses

2019 ◽  
Vol 91 (11) ◽  
pp. 1807-1820 ◽  
Author(s):  
Rayan Zaiter ◽  
Mohammad Kassem ◽  
Daniele Fontanari ◽  
Arnaud Cuisset ◽  
Chris J. Benmore ◽  
...  
Keyword(s):  
Atomic Structure ◽  
Glass Network ◽  
Ionic Transport ◽  
High Energy ◽  
X Ray Diffraction ◽  
Wide Composition Range ◽  
X Ray ◽  
Tetrahedral Environment ◽  
The Relationship ◽  
Dft Modelling

Abstract Quasi-ternary (AgI)x(HgS)0.5−x/2(GeS2)0.5−x/2 glasses, 10−4≤x≤0.6 were studied over a wide composition range covering nearly 4 orders of magnitude in the mobile cation content. The glasses show a remarkable increase of the ionic conductivity by 12 orders of magnitude and exhibit two drastically different ion transport regimes: (i) a power-law critical percolation at x≲0.04, and (ii) a modifier-controlled conductivity, exponentially dependent on x≳0.1. Using Raman spectroscopy and high-energy X-ray diffraction supported by DFT modelling of the Raman spectra we show that the glass network is essentially formed by corner-sharing CS-GeS4/2 tetrahedra. Mercury sulfide in glasses is dimorphic. The majority of Hg species (70% at x<0.2) exist as two-fold coordinated (HgS2/2)n chains. Silver species have mixed (2I+2S) tetrahedral environment forming either edge–sharing ES-Ag2I2S4/2 dimers or corner-sharing (CS-AgI2/2S2/2)n chains. The relationship between the ionic transport and atomic structure of the glasses is discussed.

scholarly journals The Low-Angle Boundaries Misorientation and Lattice Parameter Changes in the Root of Single-Crystalline CMSX-4 Superalloy Blades

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5194
Author(s):  
Robert Paszkowski ◽  
Włodzimierz Bogdanowicz ◽  
Dariusz Szeliga
Keyword(s):  
Electron Microscopy ◽  
Turbine Blades ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Single Crystalline ◽  
X Ray ◽  
The Relationship ◽  
Scanning Electron

The relationship between the angles of misorientation of macroscopic low-angle boundaries (LABs) and changes in the lattice parameter of the γ′-phase around the LABs in the root of single-crystalline (SX) turbine blades made of CMSX-4 superalloy were studied. The blades with an axial orientation of the [001] type were solidified using an industrial Bridgman furnace with a 3 mm/min withdrawal rate. X-ray diffraction topography, the EFG Ω-scan X-ray diffraction method, scanning electron microscopy, and Laue diffraction were used to study the thin lamellar samples with a thickness of 0.5 mm and orientation of the surface perpendicular to the [001] direction. It is found that in the areas with a width of a few millimetres around LABs, decreases in the lattice parameter of the γ′-phase occur. These lattice parameter changes are related to the internal stresses of the γ′-phase caused by local changes in the concentration of alloying elements and/or to the dendrite bending near the LABs. X-ray topography used on two surfaces of thin lamellar samples coupled with the lattice parameter measurements of the γ′-phase near the LAB allows separating the misorientation component of LAB diffraction contrast from the component and visualising the internal stresses of the γ′-phase.

scholarly journals Chiral 1,2-Subnaphthalocyanines

2021 ◽  
Author(s):  
Soji Shimizu ◽  
Akito Miura ◽  
Tebello Nyokong ◽  
Samson Khene ◽  
Nagao Kobayashi
Keyword(s):  
Diffraction Analysis ◽  
Magnetic Circular Dichroism ◽  
Small Variation ◽  
Soret Band ◽  
Chiral Molecules ◽  
X Ray Diffraction ◽  
Enantiomerically Pure ◽  
X Ray ◽  
First Time ◽  
The Relationship

<p>Following the first suggestion of inherent molecular chirality in asymmetrically substituted subphthalocyanines by Torres and co-workers in 2000, elucidation of the relationship between structure and chirality has become an important issue. However, separation of the enantiomers has been prevented by the low solubility of the molecules synthesized to date, and it has not been possible to link the CD signs and intensities to their absolute structures. Recently, we observed that 1,2-subnaphthalocyanines possess two diastereomers with respect to the arrangement of the naphthalene moieties and that these novel chiral molecules exhibit moderate solubility in common organic solvents. This has enabled us to separate all of the diastereomers and enantiomers. The two diastereomers have been completely characterized by NMR spectroscopy and X-ray diffraction analysis. The absorption and magnetic circular dichroism spectra, together with theoretical calculation, reveal a small variation in the frontier molecular orbitals of the 1,2-subnaphthalocyanines compared with conventional subphthalocyanines, except for destabilization of the HOMO–3, which results in a characteristic absorption in the Soret band region. The chirality of 1,2-subnaphthalcyanines, including the CD signs and intensities, is discussed in detail for the first time with enantiomerically pure molecules whose absolute structures have been elucidated by single-crystal X-ray diffraction analysis.</p>

X-ray diffraction properties of curved crystal diffractors

1992 ◽  
Vol 50 (2) ◽  
pp. 1734-1735
Author(s):  
W. Z. Chang ◽  
D. B. Wittry
Keyword(s):  
Diffraction Theory ◽  
X Rays ◽  
Diffraction Image ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Bent Crystal ◽  
Diffraction Geometry ◽  
Crystal Parameter ◽  
Quantitative Procedure

Since Du Mond and Kirkpatrick first discussed the principle of a bent crystal spectrograph in 1930, curved single crystals have been widely utilized as spectrometric monochromators as well as diffractors for focusing x rays diverging from a point. Curved crystal diffraction theory predicts that the diffraction parameters - the rocking curve width w, and the peak reflection coefficient r of curved crystals will certainly deviate from those of their flat form. Due to a lack of curved crystal parameter data in current literature and the need for optimizing the choice of diffraction geometry and crystal materials for various applications, we have continued the investigation of our technique presented at the last conference. In the present abstract, we describe a more rigorous and quantitative procedure for measuring the parameters of curved crystals.The diffraction image of a singly bent crystal under study can be obtained by using the Johann geometry with an x-ray point source.

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