bluuebunny/crossref_metadata_2025_split huggingface dataset:
The orientation relationships between widmanstatten cementite and austenite
Authors: Farooque M. , Edmonds D. V. 
Published: June 2020

Cementite has a complex orthorhombic crystalline structure with lattice parameters 4.52, 5.08 and 6.74 Å. Its crystallographic orientation relationship with austenite was first determined by Pitsch using a Hadfields Manganese Steel (nominally Fe-13Mn-1.2C (wt%))and this was later confirmed by Dippenaar and Honeycombe. This is within 5° of(where the subscripts c and a denote cementite and austenite respectively).The present study has also been carried out in Hadfields Manganese Steel, which has the advantage that it is austenitic at room temperature but can be partially decomposed to Widmanstatten cementite, among other structures, by annealing at intermediate temperatures in the approximate range 300-650 °C.An alloy of nominal composition Fe-12Mn-0.8C (wt%) was prepared as a 50 g argon arc melt and homogenised at 1200 °C. Samples were hot-rolled,cold swaged and machined to 3 mm diameter rod. Short lengths of rod were encapsulated in silica tube under a partial pressure of argon and solution treated at 1200 °C for 15 min, quenched to room temperature, and then annealed at 375 °C for 96 hours.
Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)
Authors: Zheng-fang Wang , Wang Z.F. 
Published: June 2020

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.
Precipitation of chromium borides in annealed nickel aluminides
Authors: Carro G. , Wittig J.E. , Kenik E.A. , Flanagan W.F. 
Published: June 2020

Alloys based on the intermetallic phase, Ni3Al, are a class of materials noted for superior elevated temperature mechanical properties and oxidation resistance. Boron has been shown to increase ductility in these alloys and chromium additions to boron-doped nickel aluminide alloys have been reported to improve the high temperature properties by reducing dynamic embrittlement in oxidizing environments. However, a potential problem with these Ni-Al-Cr-B alloys is the depletion of chromium and boron at grain boundaries from chromium boride precipitation.Two alloys were investigated for elevated temperature chromium boride precipitation. The first, IC-218, has the composition (at%): 16.4 Al, 8.0 Cr, 0.4 Zr, 0.1 B, Ni bal., and the second, OR3B contains 15.0 Al, 10.0 Cr, 0.1 B, Ni bal.. Samples of both alloys were rapidly solidified into circular foils, 0.25 mm thick, by splat quenching between two copper plates. Also, cold rolled and recrystallized sheet, 3 mm thick, of IC-218 was used for comparison.
Stability of the T2 phase during low-dose ion milling
Authors: Reed J. R. , Michel D. J. , Howell P. R. 
Published: June 2020

Recent studies have shown that the T2 (Al6CuLi3) phase particles in dilute Al-Li-Cu alloys transform to microcrystalline aggregates during TEM examination, during ion-beam thinning, or during in- situ heating in the TEM. Other studies, however, have noted that the T2 phase particles exhibit an ‘apparent’ five-fold symmetry suggesting that microcrystalline or twinned regions, rather than ‘single crystal’ regions, were responsible for the five-fold diffraction patterns. As a consequence, additional work was considered necessary to investigate further the stability of the T2 phase in dilute Al-Li-Cu alloys.The 3-mm diameter TEM disc specimens were prepared from a specially melted Al-2.5%Li-2.5%Cu alloy produced by conventional procedures. The TEM specimen thermal treatment and electropolishing procedures were previously reported. The electropolished disc specimens were examined in a JEOL 200CX microscope operated at 200 kV. Selected disc specimens containing the T2 phase were then subjected to ion beam thinning in a Gatan precision ion-milling system, operated with an argon ion beam, at accelerating voltage of 6 kV and a beam current of lμA.
Orientation and morphology variants of the α2 phase in B2 parent matrix in a super α2 titanium aluminide alloy
Authors: Edelson Lawrence H. 
Published: June 2020

Titanium aluminides are potential low density, high stiffness, high-temperature materials that use ordered crystal lattices to retain strength at elevated temperatures. The super α2 system is based on the hexagonal DO19 α2 phase (Ti3Al), but has sufficient β (BCC, high temperature phase) stabilizing elements (Nb, V and Mo) so that a continuous B2 ordered cubic phase is retained to room temperature. Transmission electron microscopy (TEM) images and selected area electron diffraction (SAD) patterns were used to analyze the crystallography and morphology of the α2 phase that forms when 100% B2 phase is aged at 1000°C for one hour. TEM is the only technique that provides both precise crystallographic and morphological analysis of the phase transformation.The microstructure produced from 100% B2 material, formed by ice brine quenching the super-α2 alloy from 1250°C, by aging at 1000°C for 1 hr is shown in the scanning electron micrograph in Figure 1. The dark discontinuous phase is acicular α2, while the light continuous phase is the ordered cubic B2 phase.
Microstructural stability in rapidly solidified ternary iron aluminides
Authors: Morton Allan J. , Décamps Brigitte , Gibson Mark A. , Wolfenden Alan 
Published: June 2020

Iron aluminides containing ternary additions of Cr, Si and other alloying elements offer good oxidation and sulphidation resistance at a relatively low cost but these alloys have only moderate strength at elevated temperatures and are of limited ductility. The generation of a distribution of fine dispersoids throughout the matrix of these alloys can provide increased strength and also improve ductility by reducing grain size.We report a study of the microstructural stability of rapidly solidified strip of iron aluminides containing chromium and minor additions of both titanium and boron. As cast strip thickness was in the range 80-120μm.Figure 1 shows the grain structure near the centre of the as cast strip of a 66.5Fe-28.5Al-5.0Cr (at.%) alloy. The grain size in this view of the strip is quite small (2-5μm) although optical metallography of the longitudinal and transverse cross sections show that the grain structure is columnar through much of the strip thickness.
Aging behaviour of U-6.0Wt.% Nb at temperatures above 350°C
Authors: Beverini G. , Edmonds D.V. 
Published: June 2020

Large strength increments accompanied by severe ductility losses are observed upon ageing U-6Nb at temperatures between 350°C and 450°C. This study attempts to characterize the fine scale morphological and compositional changes observed upon ageing this alloy in this temperature regime. Precipitation of Nb-rich particles having a tetragonal crystal structure is believed to be the mechanism responsible for age hardening in this alloy.Material supplied by AWE, Aldermaston, U.K. was received in the as-water quenched (WQ) condition in the form of 3 mm. diameter rods. Material was aged in sealed silica tubes containing a partial pressure of argon. The aged rods were then sliced to 0.5 mm. thick disks and subsequently ground down to a thickness of 90 μm. using 1200 grit SiC paper. Electropolishing was carried out in a Fischione twin-jet electropolishing unit using a solution of 5% HClO in methanol cooled to -60°C at a voltage of 40V.
Processing and characterization of B4C-Al laminated cermets
Authors: Yasrebi Mehrdad , Kim Gyeung H. , Milius David L. , Sarikaya Mehmet , Aksay Ilhan A. 
Published: June 2020

B4C-Al composites show enhanced fracture strength and fracture toughness values over monolithic B4C.1-2 A controlled change in structural morphologies such as lamination further enhances mechanical properties of the composite over the B4C-Al composites processed to form a monolithic morphology. This paper summarizes microstructure-property correlations studied in B4C-Al laminated composites.The laminated composite is formed either by metal infiltration of B4C tapes sandwiched with Al sheets, type (a), (Fig. 1a) or by lamination of B4C tapes of different porosity and then subjected to metal infiltration of the laminated body, type (b), (Fig. 1b). In the first method, after thin tapes of B4C were formed, each tape was individually sintered between polished graphite discs, then layered with Al sheets, and the entire stack was heated to induce infiltration. In the second method, tapes of B4C with different green densities were stacked and laminated under pressure and temperature. The laminated body was then sintered and subsequently infiltrated with Al.
TEM study of lanthanum aluminate
Authors: Yang C.Y. , Huang Z.R. , Zhou Y.Q. , Li C.Z. , Yang W.H. , Fung K.K. 
Published: June 2020

Lanthanum aluminate(LaAlO3) single crystal as a substrate for high Tc superconducting film has attracted attention recently. We report here a transmission electron microscopy(TEM) study of the crystal structure and phase transformation of LaAlO3 by using Philips EM420 and EM430 microscopes. Single crystals of LaAlO3 were investigated first by optical microscope. Stripe-shaped domains of mm size are clearly seen(Fig.1a), and 90° domain boundary is also obvious. TEM specimens were prepared by mechanical grinding and polishing followed by ion-milling.Fig.lb shows μm size stripe domains of LaAlO3. Convergent beam electron diffraction patterns (CBED) from single domain were taken.Fig. 2a and Fig. 2c are [001] zone axis patterns which show a 4mm symmetry, and the (200) dark field of this zone axis gives 2mm symmetry(fig.2b). Therefore the point group of this crystal is either 4/mmm or m3m. The projection of the first order Laue zone(FOLZ) reflections on zero layer (fig. 2c) shows that the unit cell is face centered. A tetragonal unit ceil is chosen, with a=0.532nm and c=0.753nm, c being determined from the FOLZ ring diameter.
Microstructural analyses of Si3N4 ceramics containing various sintering aids and additional Si3Ni4
Authors: Sung C.M. , Ostreicher K.J. , Buljan S.T. , Baldoni J.G. , Hefter J. 
Published: June 2020

Silicon nitride ceramics containing Al2O3 (1.5 wt%)+MgO (4 wt%) (=AM4) and Al2O3 (1.5 wt%) +Y2O3 (6 wt%)(=AY6) sintering aids together with an additional 30 v% Si3N4 have been hot pressed or hot pressed and heat-treated in an attempt to devitrify the glass phase. The expected effect of adding Si3N4 to both these formulations was to modify the glass composition in addition to the overall microstructure of the ceramics while reducing the relative amount of sintering aid. The present investigation was conducted to determine the microstructural and chemical nature of the intergranular phases present.Investigation of the intergranular phase (IGP) in the AM4-30 v% Si3N4 material indicated that the IGP was generally larger in size than the IGP in AM4 without additional Si3N4.
A TEM study of the formation of the silica structure on gel drying
Authors: Knoester Arie , Afghan Madjid 
Published: June 2020

In the manufacture of silica spheres, which are used as a support material for heterogeneous catalysts, partial drying of the silica gel proves to be a crucial step: at this stage the gel undergoes structural changes, which influence the final strength and porosity of the catalyst. Using a special preparation technique, the mechanism of these changes has been studied by means of Transmission Electron Microscopy (TEM).Silica sphere samples partially dried to different moisture contents as well as a sample of the hydrogel (the undried gel) were prepared with the aim of fixing the pore structures. To this end, the water present in the pores of the samples was replaced by a suitable plastic. This was achieved in consecutive steps: first the water was replaced by ethanol, after which the latter was replaced by a mixture of methacrylate monomers. After polymerization of the monomers ultrathin microtome slices were produced. In some cases the sectioning procedure was hampered by the presence of traces of hygroscopic sodium sulfate. This problem was overcome by introducing a washing step prior to the fixation procedure.
Texture of cholesteric cellulosic gels and films observed by electron microscopy
Authors: Giasson Julie , Revol Jean-François , Gray Derek G. 
Published: June 2020

It is now well known that cellulose derivatives form cholesteric liquid crystalline phases in the bulk and in solution. The supramolecular arrangement of the cholesteric materials gives them unique optical properties. Light entering the cholesteric domain is partially reflected. Circularly-polarized light with the same handedness as the helicoidal structure and a wavelength corresponding to the cholesteric pitch will be reflected by the mesophase. Free-standing films displaying a cholesteric order are thus strongly desirable for many different applications.Even though transmission electron microscopy (TEM) seems to be the perfect technique to extend results obtained by optical microscopy, this approach has been used infrequently in the study of liquid crystals. Liquid crystals don't lend themselves to electron microscopy because of their fluidity. Lyotropic systems are destroyed by evaporation of the solvent under high vacuum. However, under specific conditions, solid cellulosic films can retain a helicoidal organization. Classical embedding and ultra-sectioning can thus be applied on such materials as long as they do not dissolve in water.
Electron microscope studies of the plastic deformation of ternary alloys based on GaAs
Authors: Haswell R. , Bangert U. , Charsley P. 
Published: June 2020

A knowledge of the behaviour of dislocations in semiconducting materials is essential to the understanding of devices which use them . This work is concerned with dislocations in alloys related to the semiconductor GaAs . Previous work on GaAs has shown that microtwinning occurs on one of the <110> rosette arms after indentation in preference to the other . We have shown that the effect of replacing some of the Ga atoms by Al results in microtwinning in both of the rosette arms.In the work to be reported dislocations in specimens of different compositions of Gax Al(1-x) As and Gax In(1-x) As have been studied by using micro indentation on a (001) face at room temperature . A range of electron microscope techniques have been used to investigate the type of dislocations and stacking faults/microtwins in the rosette arms , which are parallel to the [110] and [10] , as a function of composition for both alloys . Under certain conditions microtwinning occurs in both directions . This will be discussed in terms of the dislocation mobility.
Direct Observation of Monolayer Zones in Al-wt 4% Cu
Authors: Jouffrey B. , Dorignac D. , Bourret A. 
Published: June 2020

Since the early works on GP zones and the model independently proposed by Preston and Guinier on the first steps of precipitation in supersaturated solid solution of aluminium containing a few percent of copper, many works have been performed to understand the structure of different stages in the sequence of precipitation.The scheme which is generally admitted can be drawn from a work by Phillips.In their original model Guinier and Preston analysed a GP zone as composed of a single (100) copperrich plane surrounded by aluminum atomic planes with a slightly shorter distance from the original plane than in the solid solution.From X-ray measurements it has also been shown that GP1 zones were not only copper monolayer zones. They could be up to a few atomic planes thick. Different models were proposed by Guinier, Gerold, Toman. Using synchrotron radiation, proposals have been recently made.
Atomic Imaging of Crystals using Large-Angle Electron Scattering in STEM
Authors: Jesson D.E. , Pennycook S. J. 
Published: June 2020

It is well known that conventional atomic resolution electron microscopy is a coherent imaging process best interpreted in reciprocal space using contrast transfer function theory. This is because the equivalent real space interpretation involving a convolution between the exit face wave function and the instrumental response is difficult to visualize. Furthermore, the crystal wave function is not simply related to the projected crystal potential, except under a very restrictive set of experimental conditions, making image simulation an essential part of image interpretation. In this paper we present a different conceptual approach to the atomic imaging of crystals based on incoherent imaging theory. Using a real-space analysis of electron scattering to a high-angle annular detector, it is shown how the STEM imaging process can be partitioned into components parallel and perpendicular to the relevant low index zone-axis.It has become customary to describe STEM imaging using the analytical treatment developed by Cowley. However, the convenient assumption of a phase object (which neglects the curvature of the Ewald sphere) fails rapidly for large scattering angles, even in very thin crystals. Thus, to avoid unpredictive numerical solutions, it would seem more appropriate to apply pseudo-kinematic theory to the treatment of the weak high angle signal. Diffraction to medium order zero-layer reflections is most important compared with thermal diffuse scattering in very thin crystals (<5nm). The electron wave function ψ(R,z) at a depth z and transverse coordinate R due to a phase aberrated surface probe function P(R-RO) located at RO is then well described by the channeling approximation;
High-Resolution Cryo-Electron Microscopy of Two-Dimensional Protein Crystals
Authors: Zemlin F. , Beckmann E. 
Published: June 2020

The task in investigating the structure of crystals is to measure the Fourier coefficients in amplitude and phase. Electron crystallography, i.e. electron diffraction combined with electron-microscopical imaging, is a straigthforward method, because there is a priori no “phase problem”. But radiation damage during electron exposure was for a long time an absolutely unbridgeable chasm on the way to high-resolution structure research of two-dimensional protein crystals by electron microscopy. Now, using cryo-electron microscopy and computer image processing, it has been proven possible to overcome this difficulty and achieve high resolution.Here we present a rough description of the recording procedure. We used a helium-cooled superconducting objective lens with 4.5 K specimen temperature, but the procedure should also be applicable at higher specimen temperatures. The radiation damage is reduced at low specimen temperature, but unfortunately there still remains a remarkable deterioration of the crystal with increasing dose, which means that minimum exposure is advisable.
Structural Study of H,K-ATPase by Electron Microscopy and Image Reconstruction
Authors: Mohraz Manijeh , Sathe Sonal , Smith P.R. 
Published: June 2020

H,K-ATPase is an integral protein of the plasma membrane of parietal cells. It is believed to constitute the pump responsible for secretion of acid into stomach. Its catalytic subunit (Mr 110,000) shows striking sequence homology to those of other transport ATPases. Recent studies suggest that there is also a glycoprotein (ca 300 amino acids) associated with the H,K pump, which is very homologous to the β subunit of the Na,K-ATPase.The enzyme is isolated in protein-rich membrane vesicles from hog stomachs. Formation of two-dimensional crystals is induced in suspensions of the enzyme by methods that had proved successful for crystallization of the Na,K-ATPase.
Unbending: Characterising Distortion and Correcting for IT
Authors: Saxton W O , Duerr R 
Published: June 2020

Unbending is becoming the fashionable alternative to simple correlation averaging, just as c-av earlier supplanted Fourier filtration or profile fitting. We note the circumstances in which it may be useful; and we recommend local real space image averaging in preference to Fourier methods.The displacement field in an image can be estimated reasonably closely from the unit cell positions indicated by cross-correlation with a ‘reference’ image patch. Correlation averaging and unbending both compensate for the displacements of unit cells as a whole, but in their standard forms do not address distortion of individual cells at all. Obviously, both can be easily adapted to do so; some such work has been reported and more is in hand. Experience suggests that correction of the displacements is indeed the most important step: these accumulate from cell to cell across the crystal.
State and Future of Electronic Image Read-OUT in TEM
Authors: Herrmann K.-H. 
Published: June 2020

The electron microscope is becoming a link in a highly sophisticated data processing system. The acquisition of image data supplied as a spatial distribution of current density requires a position sensitive electron detector which converts the current into digital information to be processed by image storages and computers to retrieve the information in which the user is interested. The ultimate goal of this interface is a lossless conversion with respect to both the number of pixels and the detection quantum efficiency (DQE) as well as high speed, minimum distortion, and linearity. I shall try to outline the present state of image read-out using both the conventional photoplate with spatial digitizing equipment and conventional TV sets. Subsequently it will be discussed how the future CCD technology (charge coupled device) may overcome some restrictions of present solutions.Every spatial recording device combines a conversion with a storage function in order to build up a signal-to-noise ratio (SNR) sufficient for detection. The following characteristics describe their performance: