bluuebunny/crossref_metadata_2025_split huggingface dataset:
Features of the subboundary structure in deformed molybdenum single crystals
Authors: Myshlyaev M.M. , Khodos I.I. , Senkov O.N. , Romanov Yu.A. 
Published: June 2020

The subboundary structure corresponding to the high temperature steady-state creep of molybdenum single crystals is formed by both regular sites of dislocation nets and walls, various in structure and composition, (the nets are formed by two, three, five and six dislocation sets having different values of the angles between the Burgers vector Ḇ and the dislocation line ū ; the walls are formed by one, two and three sets of edge and mixed dislocations; the Burgers vectors of the dislocations are I/2 <III> and, <I00>) and by the sites of a more complex and less regular structure. Several of these are considered below.Fig.I represents a subboundary formed by five dislocation sets.Its regular sites (nets) can be formed by means of interaction of dislocations I and 4 with dislocations 2 (fig.2a). In several irregular sites (fig.I and 2b) no dislocations 2 are seen to be present, and neither dislocations 3 and 5 arisen from the reactions of dislocations 2 with dislocations I and 4.
TEM examinations of ion implanted silicon using cross-section specimens
Authors: Fletcher J. , booker G.R 
Published: June 2020

Basic work is being performed on the damage structures resulting from ion implantation of (111) Si slices. Specimens were implanted at room temperature with either 60keV Ne+ in the dose range 1 x 1014 to 5 x l015 cm-2, or 150keV As+ in the range 3 x 1014 to 7.5 x 1015 cm-2, and subsequently annealed in an inert atmosphere at temperatures up to 1000°C. These were thinned for 100kV TEM examination to give both ‘plan’ and ‘90° cross-section' specimens. Results are described for four different aspects of the work.First, Fig.l shows the damage for different Ne+ doses (800°C anneal). For 2.5 x 1014( cm-2, the damage consists of a band of loops and rods, with a defect-free zone close to the surface. For 1 x 1015 cm -2, there are two separate damage layers. The upper layer comprises mainly micro-twin lamellae, and the lower layer loops and rods similar to those in Fig.la.
Surface craters induced by displacement cascades in heavy metals
Authors: Jäger W. , Merkle K. L. 
Published: June 2020

Past investigations of the erosion of surfaces under bombardment by energetic particles have mainly focused on the measurement of integral sputtering yields and the examination of surface structural changes by scanning electron microscopy. Both types of observations generally require the use of rather high particle doses (≳1015cm-2) and provide only indirect information on the primary sputtering mechanisms. For more direct information, transmission electron microscopy (TEM) was applied to study the interaction of individual displacement cascades with surfaces in thin Au films. First results from low dose (1010 - 1012cm-2) Bismuth ion irradiation revealed the existence of small craters where cascades intersect a surface. In the present paper it will be shown that this surface crater formation strongly depends on cascade energy and cascade energy density. Also, details of the observed crater contrast will be discussed in view of its implications in regard to crater formation mechanisms.Thin Au films, prepared by vacuum evaporation, were bombarded with Bismuth ions.
Observations of dislocations near θ' precipitates in neutron-irradiated Al-4% Cu by WBDF
Authors: Carpenter R. W. , Loretto M. H. , Remag  
Published: June 2020

In this paper some observations of dislocation structure in a neutron-irradiated Al—4% Cu alloy containing θ' precipitate are reported. Both weak-beam dark-field and strong-beam bright-field methods were used. During irradiation, coherency loss begins to occur, and swelling resistance decreases. The WBDF method is necessary to resolve dislocation configurations near the matrix/precipitate interfaces.The microstructure of the alloy after a neutron fluence of 2.8 x 1025 n/m2(E>0.1 MeV,T ∼ 330 K) is shown in WBDF (Fig. 1). The main features of the irradiated microstructure are the θ' precipitates, faulted and unfaulted loops with diameter ∽30 nm in the matrix, a few long dislocations lying in the precipitate/matrix interfaces, and some small (< 10 nm) contrast features in the background. The latter may be a result of the small amount of Si formed during irradiation by transmutation of the Al. Of primary present interest are dislocations in and near the interfaces.
Alignment of small He-Bubbles during in situ deformation of Al-foils
Authors: Ruedl E. , Schiller P. 
Published: June 2020

The low Z metal aluminium is a potential matrix material for the first wall in fusion reactors. A drawback in the application of A1 is the rel= atively high amount of He produced in it under fusion reactor conditions. Knowledge about the behaviour of He during irradiation and deformation in Al, especially near the surface, is therefore important.Using the TEM we have studied Al disks of 3 mm diameter and 0.2 mm thickness, which were perforated at the centre by double jet polishing. These disks were bombarded at∽200°C to various doses with α-particles, impinging at any angle and energy up to 1.5 MeV at both surfaces. The details of the irradiations are described in Ref.1. Subsequent observation indicated that in such specimens uniformly distributed He-bubbles are formed near the surface in a layer several μm thick (Fig.1).After bombardment the disks were deformed at 20°C during observation by means of a tensile device in a Philips EM 300 microscope.
Grain boundary structure observed by T.E.M
Authors: Goodhew P.J. 
Published: June 2020

This paper reports some observations on gold by TEM which imply that the dissociation of a high angle grain boundary into two lower energy boundaries may occur extensively.It is well established that grain boundaries of any desired geometry can be created in gold by the welding together of thin single crystals. The resultant thin bicrystal specimens are ideally suited for immediate examination by TEM and many aspects of grain boundary structure and behaviour in such specimens have been studied or discussed. One particularly useful specimen configuration can be achieved if the bicrystal is annealed until its boundary migrates (lowering its total area) until it is perpendicular to the surface of the thin specimen. This specimen geometry has been used to study, inter alia, the faceting of grain boundaries.During a study of the behaviour of coincidence high angle boundaries (i.e. those special boundaries whose geometry is such that a fraction 1/Σ of the lattice sites in both crystals coincide) it was noticed that the boundary under observation was no longer a single planar defect.
STEM/X-ray microanalysis across α/γ interfaces in Fe-Ni meteorites
Authors: Williams D. B. , Goldstein J. I. 
Published: June 2020

Fe-Ni meteorites have cooled at rates ∼1-10°C/106 years giving rise to a characteristic microstructure of Widmanstatten bcc α plates that have nucleated and grown from the parent fcc γ phase. This transformation results in rejection of Ni into the remaining γ, which also exhibits a variety of internal precipitation reactions. The Ni concentration at the α/γ interface should be close to the equilibrium value between the two phases and this has been determined in several meteorites, using a Philips EM300 TEM/STEM equipped with X-ray microanalytical facilities. The sharp α/γ interface also permits a practical determination to be made of the spatial resolution of the technique. This has been performed and the result compared with the predictions of two theoretical models describing the spatial resolution in terms of the spreading of the electron beam within specimens of finite thickness.Specimens of the meteorites were sectioned such that the α/γ interface was normal to the surface, then 3mm discs were spark machined, ground to ∼100 μm thick, then ion beam thinned to electron transparency
A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy
Authors: Monchoux F. , Rocher A. , Martin J.L. 
Published: June 2020

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary
Various technic for the measurement of step thickness on crystal surfaces
Authors: Boulesteix C. , Colliex C. , Mory C. , Pardo B. , Renard D. 
Published: June 2020

Contrast mechanisms, which are responsible of the various types of image formation, are generally thickness dependant. In the following, two imaging modes in the 100 kV CTEM are described : they are highly sensitive to thickness variations and can be used for quantitative estimations of step heights.Detailed calculations (1) of the bright-field intensity have been carried out in the 3 (or 2N+l)-beam symmetric case. They show that in given conditions, the two important symmetric Bloch waves interfere most strongly at a critical thickness for which they have equal emergent amplitudes (the more excited wave at the entrance surface is also the more absorbed). The transmitted intensity I for a Nd2O3 specimen has been calculated as a function of thickness t. The capacity of the method to detect a step and measure its height can be more clearly deduced from a plot of dl/Idt as shown in fig. 1.
In situ oxidation of Fe: Cr: Ni foils in the H.V.E.M
Authors: Rhoades Brian L. 
Published: June 2020

Continuous observation of oxidation processes on the surface of austenitic stainless steels has been achieved byin situoxidation of electrochemically thinned foils in the AEI EM7 H.V.E.M. using the gas reaction cell designed by Swann (1)Figure 1 shows the sequence of oxidation of a Fe: 18% Cr: 10% Ni foil at 700°C in air at 3.5 kPa recorded with an accelerating potential of 700 kV. Initially the surface reaction is characterised by the rapid formation of a transparent layer of minute randomly oriented crystals of the cubic oxide (Fe, Cr)3O4which is revealed by the appearance of diffuse rings on the single crystal γFe diffraction pattern. After approximately 30 seconds at 700γC the interface between the cubic oxide and the base alloy can be observed progressing inwards from the thinnest edges of the foil, and the formation of nuclei of α(Fe, Cr)2O3commences within the cubic oxide layer over both sides of the foil.
Ferromagnetic domains in CrBr3, investigated with a liquid helium magnetic specimen stage
Authors: Möllner H. , Schönauer M. , Hörl E.M. 
Published: June 2020

In continuation of the electron microscopical work on CrBr3 done by Matricardi et. al. we have applied a special type of liquid helium specimen stage, which has permitted application of a horizontal magnetic field in the specimen region. During observation of the specimen we have been able to apply fields up to 60 Oe, without observation fields up to 600 Oe.In general the observations of Matricardi et.al. have been confirmed, especially the contrast, size and shape of the domains, their non-appearance in in-focus micrographs and micrographs taken above the Curie point. On the other hand occasional regions of the foil, where the contrast disappears (Fig. 1a] are not thought to be chemical inhomogeneities. Such regions can exhibit strong domain contrast if the foil orientation changes slightly, as in our case by the thermal strains occuring in warming-up the specimen to approx. 60 K and cooling it down again.
SEM and Auger microanalysis studies of Cu-Be dynode surfaces at each activation condition
Authors: Koshikawa T. , Fujii Y. , Sugata E. , Kanematsu F. 
Published: June 2020

The Cu-Be alloys are widely used as the electron multiplier dynodes after the adequate activation process. But the structures and compositions of the elements on the activated surfaces were not studied clearly. The Cu-Be alloys are heated in the oxygen atmosphere in the usual activation techniques. The activation conditions, e.g. temperature and O2 pressure, affect strongly the secondary electron yield and life time of dynodes.In the present paper, the activated Cu-Be dynode surfaces at each condition are investigated with Scanning Auger Microanalyzer (SAM) (primary beam diameter: 3μmϕ) and SEM. The commercial Cu-Be(2%) alloys were polished with Cr2O3 powder, rinsed in the distilled water and set in the vacuum furnance.Two typical activation condition, i.e. activation temperature 730°C and 810°C in 5x10-3 Torr O2 pressure were chosen since the formation mechanism of the BeO film on the Cu-Be alloys was guessed to be very different at each temperature from the results of the secondary electron emission measurements.
Quantitative elemental analysis by transmission electron spectroscopy
Authors: Joy David , Maher Dennis , Mochel Peggy 
Published: June 2020

In transmission electron spectroscopy the fundamental formula for elemental quantitation using inner-shell excitations gives the number n of atoms per cm2 contributing to the K-edge aswhere Ik and Io are the integrated intensities in the K-edge and zero-loss peak, respectively. Both of these integrals are measured for a spectrometer acceptance angle 2α and an energy interval ΔE. The parameter αk(α,ΔE) is the ionization cross-section for the same angular and energy parameters. The variation of αk with α and ΔE is a function of the generalized oscillator strength and little detailed information on this quantity is available. Therefore it is necessary to proceed empirically and the simplest assumption is thatwhere σk is a saturation (x-ray) cross-section and ηα,ηΔEcan be identified with efficiency factors.The accuracy of Equation (1) for K-edges from light elements (Li ≤ Z ≤ Al) is being tested by computer curve fitting and background stripping (see Fig. 1).
X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.
Authors: Cliff G. , Nasir M.J. , Lorimer G.W. , Ridley N. 
Published: June 2020

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.
Quantitative analysis of in situ straining experiments in the case of strong frictional forces
Authors: Louchet F. , Kubin L.P. 
Published: June 2020

Investigation of frictional forces -Experimental techniques and working conditions in the high voltage electron microscope have already been described (1). Care has been taken in order to minimize both surface and radiation effects under deformation conditions.Dislocation densities and velocities are measured on the records of the deformation. It can be noticed that mobile dislocation densities can be far below the total dislocation density in the operative system. The local strain-rate can be deduced from these measurements. The local flow stresses are deduced from the curvature radii of the dislocations when the local strain-rate reaches the values of ∿ 10-4 s-1.For a straight screw segment of length L moving by double-kink nucleation between two pinning points, the velocity is :where ΔG(τ) is the activation energy and lc the critical length for double-kink nucleation. The term L/lc takes into account the number of simultaneous attempts for double-kink nucleation on the dislocation line.
A comparison of dislocation arrangements in pollycristalline aluminium deformed in uniaxial and equibiaxial tension
Authors: Parker B.A. 
Published: June 2020

There is increasing interest in understanding the deformation of sheet metals in stress systems similar to those used in metal-forming practice. Parameters in constitutive equations describing plastic deformation are found to be sensitive to the strain path and the present work describes experiments aimed at elucidating differences in the micromechanics of deformation.Samples of annealed, 1-mm thick, commercial purity,aluminium sheet with a grain size of 30 μm were deformed at a strain rate of 2x10-3 sec-1 to natural strains in the range 0.03 to 0.16 in uniaxial and in balanced biaxial tension. Strains were measured at the site of the electron microscope samples using a 2-mm electroetched grid; the original rolling direction of the sheet was identified on the specimen discs.There are difficulties in drawing conclusions from the structures observed because of the inhomogeneity of plastic deformation, particularly at low strains and because of the relaxation of the deformed structure during sample preparation.
Microanalysis of precipitates in a ferritic steel
Authors: Titchmarsh J.M. 
Published: June 2020

The advances in recent years in the microanalytical capabilities of conventional TEM's fitted with probe forming lenses allow much more detailed investigations to be made of the microstructures of complex alloys, such as ferritic steels, than have been possible previously. In particular, the identification of individual precipitate particles with dimensions of a few tens of nanometers in alloys containing high densities of several chemically and crystallographically different precipitate types is feasible. The aim of the investigation described in this paper was to establish a method which allowed individual particle identification to be made in a few seconds so that large numbers of particles could be examined in a few hours.A Philips EM400 microscope, fitted with the scanning transmission (STEM) objective lens pole-pieces and an EDAX energy dispersive X-ray analyser, was used at 120 kV with a thermal W hairpin filament. The precipitates examined were extracted using a standard C replica technique from specimens of a 2¼Cr-lMo ferritic steel in a quenched and tempered condition.
Application of convergent beam electron microscopy in materials science
Authors: Steeds J.W. , Fung K. K. 
Published: June 2020

IntroductionWe have used a Philips EM400 electron microscope with a STEM pole- piece to carry out convergent beam electron microscopy on a wide variety of materials, including precipitates in stainless steels, metal/semiconductor contacts, metal oxide catalysts, environmental fibres, metastable phases in evaporated films, and transition metal chalcogenide layer compounds. Two features of this microscope make it particularly suitable for convergent beam work. These are its low hydrocarbon partial pressure which greatly reduces the carbon contamination of the specimen when working with a small probe (̴ 300 Ådiameter) and the very wide angular field of view in the diffraction plane (̴ 16°).Two-dimensional diffraction may be used to yield information about the projected crystal potential. In certain cases a simple relationship has been established between the form of zone axis patterns and the nature of the projected potential, Oneway of using this information is by making measurements of zone axis critical voltages and we have recently extended our measurements to a number of zone axis patterns with 6 mm symmetry having different sorts of projected potential.
A new method of complex structure analysis by electron microscopy
Authors: Rybin V.V. , Voronina E.V. 
Published: June 2020

Recently, it has become essential to develop a helpful method of the complete crystallographic identification of fine fragmented crystals. This was maainly due to the investigation into structural regularity of large plastic strains. The method should be practicable for determining crystallographic orientation (CO) of elastically stressed micro areas of the order of several micron fractions in size and filled with λ>1010 cm-2 density dislocations or stacking faults. The method must provide the misorientation vectors of the adjacent fragments when the angle ω changes from 0 to 180° with the accuracy of 0,3°. The problem is that the actual electron diffraction patterns obtained from fine fragmented crystals are the superpositions of reflections from various fragments, though more than one or two reflections from a fragment are hardly possible. Finally, the method should afford fully automatic computerized processing of the experimental results.The proposed method meets all the above requirements. It implies the construction for a certain base position of the crystal the orientation matrix (0M) A, which gives a single intercorrelation between the coordinates of the unity vector in the reference coordinate system (RCS) and those of the same vector in the crystal reciprocal lattice base : .
New orientation relationship in martensitic transformation in austenitic stainless steel welded explosively
Authors: Yamashita T. , Onzawa T. 
Published: June 2020

Martensitic transformation induced by plastic deformation in 18/8 stainless steel has been extensively investigated by many workers. Venablel has proposed that the orientation relationships in transformations are (111)γ// (00.1)ε// (011)α and [101]γ//[11.0]ε//[lll]α. Since metals welded explosively or shock loaded are subjected to rapid plastic deformation under a high pressure, the aspects of martensitic transformations are expected to be different from those reported hitherto. The purpose of the present experiment is to show the new orientation relationship in transformation and the new aspects of transformations in 18/8 stainless steel welded explosively as well as shock loaded. The atomic movements required in transformation are also considered.Austenitic stainless steel plates, 3×50×200 mm, were heated in vacuum at about 700°C for 30 min to transform existing ε and α phases into γ phase. They were welded explosively by using two kinds of explosives with detonation velocities of 2,400 m/s and 5,000 m/s.
TEM - characterization of precipitates in Al-Zn5-Mgl
Authors: Degischer H.P. , Lacom W. 
Published: June 2020

Various techniques of TEM are described to investigate precipitates in metals, which reach dimensions from a few nm to more than 100 nm. The examples presented here are characterized by strong interactions of the lattice structures of the inclusions and the matrix, therefore replica techniques are not applicable (an example of that is presented in [1]] because the metastable phases might change.Selected area diffraction of regions of about 100 nm give well defined diffraction patterns of the phases present in that part of the specimen. Generally the diagram corresponding to a single precipitate cannot be obtained, but in contrast to microdiffraction techniques sharp diffraction spots can be measured. The orientation relationship between the inclusions and the matrix can be studied best, if the beam direction coincides with the main cristallographic zone axis, i.e. in cubic lattices: <001>, <112>, <111>, <011>. At these poles the patterns are highly symmetric, especially because of doublediffraction, but the diagram can be constructed to unfold the coinciding patterns.