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Equal channel angular extrusion (ECAE) of 49Fe-49Co-2V, also known as Hiperco® 50A or Permendur-2V, greatly improves the strength and ductility of this alloy, while sacrificing soft magnetic performance. ECAE Hiperco specimens were subjected to post-ECAE annealing in order to improve soft magnetic properties. The microstructure, mechanical properties, and magnetic performance are summarized in this study. Annealing begins above 650°C and a steep decline in yield strength is observed for heat treatments between 700 and 840°C due to grain growth and the Hall-Petch effect, although some strength benefit is still observed in fully annealed ECAE material compared to conventionally processed bar. Soft magnetic properties were assessed through B-H hysteresis curves from which coercivity (Hc) values were extracted. Hc decreases rapidly with annealing above 650°C as well, i.e. improved soft magnetic behavior. The observed trend is attributed to annealing and grain growth in this temperature regime, which facilitates magnetic domain wall movement. The coercivity vs. grain size results generally follow the trend predicted in the literature. The magnetic behavior of annealed ECAE material compares favorably to conventional bar, possibly due to mild crystallographic texturing which enhances properties in the post-ECAE annealed material. Overall, this study highlights a definitive tradeoff between mechanical and magnetic properties brought about by post-ECAE annealing and grain growth. ®Hiperco is a tradename of Carpenter Technology Corp., Reading, PA.

Ion beams are now widely used to thin, shape, or cut materials on the submicrometer scale. This is possible because ions can sputter (i.e., physically remove) material from the target. Ions can also be used to image materials because the incident beam generates ion-induced secondary electrons (iSE). In both cases, the nature of the target material and the choice of the ion employed and its initial energy will determine not only how quickly the beam can thin a specimen, but also the resolution and contrast of the iSE image that is generated. Clearly, there is a need to be able to predict parameters, such as the nature, information content, and spatial resolution of the iSE image. These and other related questions have been investigated using Monte Carlo simulations. We show how the parameters defining quantities, such as depth of penetration and the energy deposited by the incident beam, or the signal yield and resolution of the iSE image, can be predicted using this approach and how these results make it possible to interpret data and optimize operating conditions.

We report analyses of 14 group IVA iron meteorites, and the ungrouped but possibly related, Elephant Moraine (EET) 83230, for siderophile elements by laser ablation ICP-MS and isotope dilution. EET was also analyzed for oxygen isotopic composition and metallographic structure, and Fuzzy Creek, currently the IVA with the highest Ni concentration, was analyzed for metallographic structure. Highly siderophile elements (HSE) Re, Os and Ir concentrations vary by nearly three orders of magnitude over the entire range of IVA irons, while Ru, Pt and Pd vary by less than factors of five. Chondrite normalized abundances of HSE form nested patterns consistent with progressive crystal–liquid fractionation. Attempts to collectively model the HSE abundances resulting from fractional crystallization achieved best results for 3 wt.% S, compared to 0.5 or 9 wt.% S. Consistent with prior studies, concentrations of HSE and other refractory siderophile elements estimated for the bulk IVA core and its parent body are in generally chondritic proportions. Projected abundances of Pd and Au, relative to more refractory HSE, are slightly elevated and modestly differ from L/LL chondrites, which some have linked with group IVA, based on oxygen isotope similarities. Abundance trends for the moderately volatile and siderophile element Ga cannot be adequately modeled for any S concentration, the cause of which remains enigmatic. Further, concentrations of some moderately volatile and siderophile elements indicate marked, progressive depletions in the IVA system. However, if the IVA core began crystallization with � 3 wt.% S, depletions of more volatile elements cannot be explained as a result of prior volatilization/condensation processes. The initial IVA core had an approximately chondritic Ni/Co ratio, but a fractionated Fe/Ni ratio of � 10, indicates an Fedepleted core. This composition is most easily accounted for by assuming that the surrounding silicate shell was enriched in iron, consistent with an oxidized parent body. The depletions in Ga may reflect decreased siderophilic behavior in a relatively oxidized body, and more favorable partitioning into the silicate portion of the parent body. Phosphate inclusions in EET show D 17 O values within the range measured for silicates in IVA iron meteorites. EET has a typical ataxitic microstructure with precipitates of kamacite within a matrix of plessite. Chemical and isotopic evidence for a genetic relation between EET and group IVA is strong, but the high Ni content and the newly determined, rapid cooling rate of this meteorite show that it should continue to be classified as ungrouped. Previously reported metallographic cooling rates for IVA iron meteorites have been interpreted to indicate an inwardly crystallizing, � 150 km radius metallic body with little

One of the most important applications of a focused ion beam (FIB) workstation is preparing samples for transmission electron microscope (TEM) investigation. Samples must be uniformly thin to enable the analyzing beam of electrons to penetrate. The FIB enables not only the preparation of large, uniformly thick, sitespecific samples, but also the fabrication of lamellae used for TEM samples from composite samples consisting of inorganic and organic materials with very different properties. This article gives an overview of the variety of techniques that have been developed to prepare the final TEM specimen. The strengths of these methods as well as the problems, such as FIB-induced damage and Ga contamination, are illustrated with examples. Most recently, FIB-thinned lamellae were used to improve the spatial resolution of electron backscatter diffraction and energy-dispersive x-ray mapping. Examples are presented to illustrate the capabilities, difficulties, and future potential of FIB.

Dynamic control of thermal transport in solid-state systems is a transformative capability with the promise to propel technologies including phononic logic, thermal management, and energy harvesting. A solid-state solution to rapidly manipulate phonons has escaped the scientific community. We demonstrate active and reversible tuning of thermal conductivity by manipulating the nanoscale ferroelastic domain structure of a Pb(Zr0.3Ti0.7)O3 film with applied electric fields. With subsecond response times, the room-temperature thermal conductivity was modulated by 11%.

A potentially more cost-efficient method of growing single-crystal relaxor-based ferroelectric materials has been investigated. Seed single crystals of Pb(Mg1/3Nb2/3)O3(PMN)—;35 mol% PbTiO3(PT) were embedded within polycrystalline powders and annealed at temperatures from 900° to 1200°C. The boundary of the single crystal migrated through the polycrystal matrix under the influence of grain boundary curvature; growth distances of several millimeters were observed, verifying the feasibility of the approach. The grown single crystals exhibited macroscopic cubic growth morphologies with (100) faces. Strain levels as high as 0.68% under an electric field of 30 kV/cm were observed in initial measurements.

The identification of crystallographic phases in the scanning electron microscope (SEM) has been limited by the lack of a simple way to obtain electron diffraction data of an unknown while observing the microstructure of the specimen. With the development of charge coupled device (CCD)-based detectors, backscattered electron Kikuchi patterns, alternately referred to as electron backscattered diffraction (EBSD) patterns, can be easily collected. Previously, EBSD has been limited to crystallographic orientation studies due to the poor pattern quality collected with video rate detector systems. With CCD detectors, a typical EBSD can now be acquired from a micron or submicron sized crystal using an exposure time of 1–10 s with an accelerating voltage of 10–40 kV and a beam current as low as 0.1 nA. Crystallographic phase analysis using EBSD is unique in that the properly equipped SEM permits high magnification images, EBSDs, and elemental information to be collected from bulk specimens. EBSD in the SEM has numerous advantages over other electron beam-based crystallographic techniques. The large angular view (∼70°) provided by EBSD and the ease of specimen preparation are distinct advantages of the technique. No sample preparation beyond what is commonly used for SEM specimens is required for EBSD.

The application of focused ion beam techniques to prepare cross-sections of wear tracks is presented. Electron backscatter diffraction analysis of wear scars on electroformed Ni revealed the formation of two subsurface zones, each with its own characteristic features. Formation of low-angle grain boundaries and spread in the orientation of pole figures were also observed.

Spectral imaging in the scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer has the potential to be a powerful tool for chemical phase identification, but the large data sets have, in the past, proved too large to efficiently analyze. In the present work, we describe the application of a new automated, unbiased, multivariate statistical analysis technique to very large X-ray spectral image data sets. The method, based in part on principal components analysis, returns physically accurate (all positive) component spectra and images in a few minutes on a standard personal computer. The efficacy of the technique for microanalysis is illustrated by the analysis of complex multi-phase materials, particulates, a diffusion couple, and a single-pixel-detection problem.

Lithographic, Galvanoformung, Abformung (LIGA) component fabrication is a process in which structural material is deposited into a patterned polymethyl-methacrylate (PMMA) mold realized through deep X-ray lithography. The process permits fabrication of metal microelectrome chanical systems (MEMS) components with representative dimensions that range from a few microns to several millimeters. This investigation characterizes the microstructure and mechanical properties of LIGA-fabricated nickel (LIGA Ni), electrodeposited using Watts bath and sulfamate bath chemistries. As a prelude to studying high-temperature joining processes in LIGA Ni components, an annealing investigation was conducted on samples fabricated from both bath chemistries. Mechanical properties and microstructural analyses on as-deposited and annealed samples were conducted using a mini servohydraulic load frame and the electron backscatter diffraction (EBSD) microtexture measurement technique. The deposits were found to have fine-grain, highly textured microstructures oriented with an acicular or columnar morphology relative to the plating direction. Previously uncharacterized, anomalous, local spatial variations in the crystallographic texture of the as-deposited microstructures were identified by EBSD analyses. Microstructural evolution during annealing seemed to follow a recovery, recrystallization, rapid grain-growth microstructural-evolution mechanism in LIGA Ni deposited from the Sulfamate bath chemistry and simply a recovery and grain-growth microstructural-evolution mechanism in LIGA Ni deposited from the Watts bath chemistry. The evolution of microstructure in the annealed samples corresponded with a dramatic drop in their strength and determined the limiting diffusion-bonding temperature for LIGA Ni components.

An S-phase intermetallic compound (Al{sub 2}CuMg) was synthesized in bulk form to characterize its electrochemical behavior by conventional techniques. Large S-phase crystals, suitable for analysis, were formed in an Al-Cu-Mg ingot. The structure of Al{sub 2}CuMg was verified by electron-backscatter Kikuchi patterns and X-ray diffraction. The composition of Al{sub 2}CuMg was verified by electron-probe microchemical analysis. Open-circuit potential and potentiodynamic polarization measurements were conducted in aerated and deaerated 0.5 M NaCl solutions. Bulk S-phase electrodes exhibited steady-state open-circuit potentials ranging from {minus}0.920 to {minus}0.930 V{sub SCE}, which did not vary significantly with changes in solution aeration. In aerated solutions, the phase dissolved vigorously at modest anodic polarizations, and no passive response was detected. Limiting cathodic current densities on the order of 1.0 mA/cm{sup 2} were measured for small cathodic polarizations, probably due to the development of a porous, catalytic surface. Overall, the S phase supports rapid anodic and cathodic reaction kinetics, which contribute to the instability of the compound and subsequent liberation of Cu. These results implicate the presence of S-phase intermetallic particles as a key contributor to the poor corrosion resistance of Al-Cu-Mg alloys.

The solidification reaction sequences of experimental superalloys containing systematic variations in Fe, Nb, Si, and C were studied using differential thermal analysis (DTA) and microstructural characterization techniques. The reaction sequences responsible for microstructural development were found to be similar to those expected in the Ni-Nb-C ternary system and commercial superalloys of comparable composition. The solute-rich interdendritic liquid generally exhibited two eutectic-type reactions at the terminal stages of solidification: L → (γ+NbC) and L → (γ+Laves). The Ni-base alloys with a high C/Nb ratio represented the only exception to this general solidification sequence. This group of alloys terminated solidification with the L → (γ + NbC) reaction and did not exhibit the γ/Laves constituent. At similar levels of solute elements (Nb, Si, and C), the Fe-base alloys always formed more of the γ/Laves eutectic-type constituent than the corresponding Ni-base alloys. Silicon additions also increased the amount of the γ/Laves constituent that formed in the assolidified microstructure, while C additions promoted formation of γ/NbC. The influence of Nb was dependent on the C content of the alloy. When the C content was low, Nb additions generally promoted formation of γ/Laves, while Nb additions to alloys with high C led to formation of the γ/NbC constituent. The results of this work are combined with quantitative analyses for developing γ-Nb-C pseudoternary solidification diagrams in a companion article.

Backscattered electron Kikuchi patterns (BEKP) suitable for crystallographic phase analysis can be collected in the scanning electron microscope (SEM) with a newly developed charge coupled device (CCD) based detector. Crystallographic phase identification using BEKP in the SEM is unique in that it permits high magnification images and BEKPs to be collected from a bulk specimen. The combination of scanning electron microscope (SEM) imaging, BEKP, and energy dispersive x-ray spectrometry holds the promise of a powerful new tool for materials science.

A parallel implementation of a Monte Carlo algorithm for modeling the scattering of electrons in solids and the resulting X-ray production is described. Two important issues for accurate and fast parallel simulation are discussed-random number generation and load-balancing. Timing results for the parallel simulation are given which show even modest-sized parallel machines can be competitive with conventional vector supercomputers for Monte Carlo trajectory simulations. Examples of parallel calculations performed to analyze specimen composition data and to characterize electron microscope performance are briefly highlighted.

X-ray spectra and Z-contrast images have been obtained from thin foils of off-stoichiometric Ni3Al both with and without boron. The results show that grain boundaries in nickel-rich Ni3Al are nickel-enriched and that the addition of boron increases this nickel enrichment. The nickel enrichment is present as a second phase along some boundaries in undoped material and along all boundaries in boron-doped material. The phase is shown, using convergent-beam electron diffraction, to be disordered and to have the same orientation as one of the adjacent grains. By comparison, grain boundaries in aluminium-rich Ni3Al, either with or without boron, have compositions that are similar to the matrix. Correspondingly, a second phase was not found along the grain boundaries of this alloy.

SUMMARY The X-ray microanalytical spatial resolution is determined experimentally in various analytical electron microscopes by measuring the degradation of an atomically discrete composition profile across an interphase interface in a thin-foil of Ni-Cr-Fe. The experimental spatial resolutions are then compared with calculated values. The calculated spatial resolutions are obtained by the mathematical convolution of the electron probe size with an assumed beam-broadening distribution and the single-scattering model of beam broadening. The probe size is measured directly from an image of the probe in a TEM/STEM and indirectly from dark-field signal changes resulting from scanning the probe across the edge of an MgO crystal in a dedicated STEM. This study demonstrates the applicability of the convolution technique to the calculation of the microanalytical spatial resolution obtained in the analytical electron microscope. It is demonstrated that, contrary to popular opinion, the electron probe size has a major impact on the measured spatial resolution in foils < 150 nm thick.

Silicon-deoxidized, tempered bainitic 1 percent CrMoV steel is currently used extensively for high-temperature steam turbine rotor forgings operating at temperatures up to 565°C due to its excellent creep rupture properties and relative economy. There is impetus to improve the creep rupture strength of this steel while maintaining its current toughness level and vice versa. The excellent creep rupture ductility of the low Si version of this steel allows the use of a higher austenitizing temperature or tensile strength level for improving creep rupture strength without loss in creep ductility or toughness. When the tensile strength of this steel is increased from 785 to 854 MPa, the creep rupture strength exceeds that of the more expensive martensitic 12CrMoVCbN steel currently used for high-temperature rotor applications where additional creep rupture strength is required. The toughness of 1 percent CrMoV steel is improved by lowering the bainite start (Bs) temperature in a “superclean” base composition which is essentially free of Mn, Si, P, S, Sb, As and Sn. The Bs temperature can be lowered through the addition of alloying elements (i.e., C, Ni, Cr, and Mo) and/or increasing the cooling rate from the austenitizing temperature. Using these techniques, the 50 percent FATT can be lowered from approximately 100°C to below room temperature, which provides the opportunity to eliminate the special precautionary procedures currently used in the startup and shutdown of steam turbines. The most promising steels in terms of creep rupture and toughness properties contain 2.5 percent Ni and 0.04 percent Cb (for austenite grain refinement and enhanced tempering resistance). In general, the creep rupture strength of the superclean steels equals or exceeds that of the standard 1 percent CrMoV steel. In addition, the superclean steels have not been found to be susceptible to temper embrittlement, nor do they alter the room temperature fatigue crack propagation characteristics of the standard 1 percent CrMoV steel. These new steels may also find application in combination high-temperature-low-temperature rotors and gas turbine rotors.

A series of resolved α-acetylenic pyrrolidinyl, piperidinyl and perhydroazepinyl derivatives has been synthesized by a facile route including a key anodic oxidation step. Assignments of absolute configurations were based on chemical correlation and circular dichroism spectroscopy.

EBSD should now be considered a standard analytical accessory for the SEM. The spatial resolution of EBSD is quite high (as high as a few nm, depending upon material) and is suitable for the study of many nano-crystalline materials. For applications of EBSD where the highest spatial resolution is required, an SEM with a field emission electron source is mandatory as the resolution of the technique is most directly determined by the electron beam size. Further developments the electron optics of the SEM should allow even higher spatial resolutions. For nano-crystalline materials, EBSD is most useful for the mapping of grain orientations and grain boundary misorientations as demonstrated in the examples shown in this chapter.

A comprehensive three-dimensional ~3D! microanalysis procedure using a combined scanning electron microscope ~SEM!/focused ion beam ~FIB! system equipped with an energy-dispersive X-ray spectrom- eter ~EDS! has been developed. The FIB system was used first to prepare a site-specific region for X-ray microanalysis followed by the acquisition of an electron-beam generated X-ray spectral image. A small section of material was then removed by the FIB, followed by the acquisition of another X-ray spectral image. This serial sectioning procedure was repeated 10-12 times to sample a volume of material. The series of two-spatial- dimension spectral images were then concatenated into a single data set consisting of a series of volume elements or voxels each with an entire X-ray spectrum. This four-dimensional ~three real space and one spectral dimension! spectral image was then comprehensively analyzed with Sandia's automated X-ray spectral image analysis software. This technique was applied to a simple Cu-Ag eutectic and a more complicated localized corrosion study where the powerful site-specific comprehensive analysis capability of tomographic spectral imaging ~TSI! combined with multivariate statistical analysis is demonstrated.

A database of mechanical properties for weldment fusion and heat-affected zones was established for AerMet{reg_sign}100 alloy, and a study of the welding metallurgy of the alloy was conducted. The properties database was developed for a matrix of weld processes (electron beam and gas-tungsten arc) welding parameters (heat inputs) and post-weld heat treatment (PWHT) conditions. In order to insure commercial utility and acceptance, the matrix was commensurate with commercial welding technology and practice. Second, the mechanical properties were correlated with fundamental understanding of microstructure and microstructural evolution in this alloy. Finally, assessments of optimal weld process/PWHT combinations for cotildent application of the alloy in probable service conditions were made. The database of weldment mechanical properties demonstrated that a wide range of properties can be obtained in welds in this alloy. In addition, it was demonstrated that acceptable welds, some with near base metal properties, could be produced from several different initial heat treatments. This capability provides a means for defining process parameters and PWHT's to achieve appropriate properties for different applications, and provides useful flexibility in design and manufacturing. The database also indicated that an important region in welds is the softened region which develops in the heat-affected zone (HAZ) and analysis within the welding metallurgy studies indicated that the development of this region is governed by a complex interaction of precipitate overaging and austenite formation. Models and experimental data were therefore developed to describe overaging and austenite formation during thermal cycling. These models and experimental data can be applied to essentially any thermal cycle, and provide a basis for predicting the evolution of microstructure and properties during thermal processing.

Although oxidants such as superoxide (O2.) and hydrogen peroxide (H2O2) play a role in host-mediated destruction of foreign pathogens yet excessive generation of oxidants may lead to a variety of pathological complications in the cardiovascular system. An important mechanism by which oxidants cause dysfunction of the cardiovascular system appears to be due to the increase in intracellular free Ca2+ concentration. Oxidants cause cellular Ca2+ mobilization by modulating activities of a variety of regulators such as Na+/H+ and Na+/Ca2+ exchangers, Na+/K+ ATPase and Ca2+ ATPase and Ca2+ channels that are associated with Ca2+ transport in the plasma membrane and the sarco(endo)plasmic reticular membrane of myocardial cells. Recent research have suggested that the increase in Ca2+ level by oxidants plays a pivotal role in inducing several protein kinases such as protein kinase C, tyrosine kinase and mitogen activated protein kinases. Oxidant-mediated alteration of different signal transduction systems and their interations eventually regulate a variety of pathological conditions such as atherosclerosis, apoptosis and necrosis in the myocardium.

Treatment of bovine pulmonary artery smooth muscle tissue microsomes with H2O2 (1 mM) markedly stimulated protease activity tested with a synthetic substrate N-benzoyl-DL-arginine p-nitroanilide (BAPNA), and also enhanced Ca(2+)-ATPase activity. ATP-dependent Ca(2+) uptake was found to be stimulated upon treatment of the microsomes with H2O2. Pretreatment of the microsomes with vitamin E and aprotinin prevented the H2O2-induced stimulation of Ca(2+)-ATPase activity and also ATP-dependent Ca(2+) uptake. In contrast, H2O2-induced inhibition of Na(+)-dependent Ca(2+) uptake was reversed by vitamin E and aprotinin.

The addition of an energy dispersive x-ray spectrometer to the ultra-high vacuum (UHV) environment present in many modern electron microscopes should be done under two major constraints. First, the addition of the spectrometer should not compromise the UHV environment in the specimen chamber, and second, the vacuum environment of the electron microscope should not compromise the performance of the spectrometer. Thus, the successful addition of an EDS to a UHV vacuum system requires an understanding of UHV and of how the constituents of the vacuum can affect the performance and the sensitivity of the EDS. Materials used in the construction of the spectrometer as well as the mechanical design of the spectrometer must be compatible with UHV conditions.

Electron backscatter diffraction (EBSD) in the SEM has become a widely used technique for both automated orientation mapping and the identification of unknown crystalline phases. Despite the rapidly growing use of this technique for the above applications, there has been relatively little fundamental research concerned with determining the thickness of the surface layer that generates the EBSD pattern. EBSD patterns are related through reciprocity to electron channeling patterns. Based on this assumption the thickness of the surface layer that an EBSD pattern is generated in is 2 or 3 extinction distances. Extinction distances at low SEM voltages (10-20 kV) are quite short. Thus, EBSD patterns are generated in very thin surface layers. This paper will discuss the results of a study of the information depth of EBSD in the SEM.Previous research has attempted to determine the information depth of EBSD by obtaining patterns from samples that have had layers of other crystalline or microcrystalline material deposited on the surface.

Exposure of rabbit pulmonary arterial smooth muscle cells to hydrogen peroxide cause dose-dependent stimulation of [14C] arachidonic acid (AA) release and enhancement of the cell membrane-associated phospholipase A2 activity as well as of the cell membrane-bound serine esterase activity tested against synthetic substrate p-tosyl-L-arginine methyl ester. While pretreatment of cells with serine protease inhibitors, viz. phenyl methyl sulphonyl fluoride, diisopropyl fluorophosphate and alpha-1-proteinase inhibitor, and antioxidant vitamin E prevents H2O2 stimulation of AA release and the cell membrane-bound serine esterase and PLA2 activities, that with actinomycin D and cycloheximide is devoid of any effect on H2O2 caused stimulation of AA release and the smooth muscle cell membrane associated serine esterase and PLA2 activities. Treatment of the smooth muscle cell membrane suspension with the serine protease trypsin markedly stimulates PLA2 activity. These results suggest that on exposure to H2O2 the smooth muscle cell membrane-bound serine esterase plays an important role in stimulating the cell membrane associated PLA2 activity thereby resulting in an increase in AA release.

Electron backscatter diffraction (EBSD) is a technique that can provide identification of unknown crystalline phases while exploiting the excellent imaging capabilities of the scanning electron microscope (SEM). Phase identification using EBSD has now progressed to the point that it is commercially available. Phase identification in the SEM requires high quality EBSD patterns that can only be collected using either film or charge coupled device (CCD)-based cameras. High quality EBSD patterns obtained in this manner show many diffraction features that are useful in the determination of the unit cell of the sample.’ This paper will discuss the features in the EBSD patterns and the procedure used to determine the reduced unit cell of the sample.One of the major advantages of EBSD over electron diffraction in the transmission electron microscope is the remarkable field of view that is routinely attained. The large angular view of the diffraction pattern permits many zone axes and their associated symmetries to be viewed in a single pattern or at most a few patterns.

The technique of electron backscatter diffraction (EBSD) in the scanning electron microscope is becoming a standard technique for the characterization of materials. EBSD has evolved into a tool that can determine the orientation of a crystalline area of interest or the technique can be used for the identification of unknown phases from their composition and crystallography. The application of the technique to ceramic materials has demonstrated the many advantages of this technique over classical x-ray diffraction techniques or electron diffraction in the TEM.EBSD patterns are obtained by illuminating a highly tilted sample (>45° from horizontal) with a stationary electron beam. Electrons that are backscattered from the sample may satisfy the condition for channeling (or diffraction) and produce images that contain bands of increased and decreased intensity that are equivalent to channeling patterns. The patterns are imaged by placing a phosphor screen near the sample and imaging the screen with either TV rate or a slow scan CCD camera.

Phase identification using electron backscatter diffraction (EBSD) in the SEM has become a useful and important tool for the characterization of crystalline materials. Phase identification is accomplished using EBSD in the following manner. First, a high quality camera must be added to the SEM. Suitable cameras use slow scan CCD imagers coupled either by a lens or a fiber optic bundle to a phosphor screen that is situated near the sample. A EBSD pattern is collected and EDS or WDS is used to determine qualitatively the chemistry of the area. An automated routine is then used to extract the positions and widths of the lines in the pattern followed by a calculation of the unit cell volume. This information coupled with the chemistry of the sample is then used to search a database of crystal structures. Currently, the ICDD's Powder Diffraction file of over 100,000 compounds is used. Once a list of potential matches is found the patterns are indexed and then simulated to demonstrate that the phase has been identified. This paper will demonstrate use of EBSD for phase identification and then will speculate on future developments.A particularly nice application of EBSD is the use of the technique for the identification of phases that form in welds. Figure 1a is an EBSD pattern obtained from a acicular phase in a superalloy weld. The phase was determined to be primarily Ti and Ni. Analysis of the patterns showed that the phase is Ni3Ti. Figure 1b shows the simulation for Ni3Ti overlaid on the experimental pattern demonstrating that the phase has been identified.

Energy-dispersive x-ray spectrometry (EDS) with a SiLi detector has become a standard technique in the analytical electron microscope (AEM). There have been many difficulties to overcome involving both the interfacing of the spectrometer to the microscope and in developing robust techniques for quantitative analysis of thin specimens. The AEM is a difficult environment for EDS due to the high accelerating voltages (100-400 kV) typically used and due to constraints on detector placement relative to the specimen as a result of the confined space within the specimen region of the AEM. The first published account of the installation of SiLi EDS on a transmission electron microscope (TEM) occurred in 1969. In this paper and subsequent publications, these authors described many of the difficulties that still haunt EDS in the AEM.The initial attempts at interfacing EDS to a TEM column demonstrated that the. specimen stage of a TEM was not ideal for this purpose.

This tutorial will describe the technique of electron backscattered diffraction (EBSD) in the scanning electron microscope (SEM). To properly exploit EBSD in the SEM it is important to understand how these patterns are formed. This discussion will be followed by a description of the hardware required for the collection of electron backscatter patterns (EBSP). We will then discuss the methods used to extract the appropriate crystallographic information from the patterns for orientation determination and phase identification and how these operations can be automated. Following this, a number of applications of the technique for both orientation studies and phase identification will be discussed.EBSD in the SEM is a phenomenon that has been known for many years. EBSD in the SEM is a technique that permits the crystallography of sub-micron sized regions to be studied from a bulk specimen. These patterns were first observed over 40 years ago, before the development of the SEM and were recorded using a special chamber and photographic film.

Monte Carlo electron trajectory simulations have been adapted to run on massively parallel supercomputers. An nCUBE2 parallel supercomputer with 1024 processors has been used in these studies. The advantage of the parallel architecture is the great increase in computational speed and the fact that few changes in the standard serial Monte Carlo algorithms are required. The temporal performance of the massively parallel Monte Carlo electron trajectory simulation run on 1024 nodes has been compared with Monte Carlo codes run on other types of supercomputers (CRAY-YMP). It was found to be as much as 100 times faster than the CRAY-YMP and over 2000 times faster than a VAX 785. This increase in computational speed allows the exploration of problems, in particular those involving small probability events, which are not normally amenable to solution by traditional serial Monte Carlo simulations due tothe time intensive nature of the calculations. For example, the calculation of 1,000,000 electrons at 100 kV through a thin foil takes about 6 seconds on the nCUBE.

The use of the recently developed charge coupled device (CCD)-based detector for the acquisition of high quality backscattered electron Kikuchi patterns (BEKP) has allowed on-line crystallographic phase identification studies to be conducted in the scanning electron microscope. High quality patterns suitable for analysis have been obtained in a wide variety of materials with little special specimen preparation. Phase identification through a combination of BEKP and energy dispersive x-ray spectrometry (EDS) is demonstrated by the identification of crystals present on ruthenium oxide thin films on Si. The crystals were identified as RuO2, a tetragonal phase.The CCD-based detector has been described previously and will only be briefly described here. The detector consists of a scientific grade slow scan CCD coupled to a YAG scintillator by a fiber optic reducer. During operation the CCD is cooled to -40°C by a thermoelectric cooler. This detector allows high quality patterns to be recorded with beam currents as low as 10-10A and exposure times of 1 to 10 seconds.

There have been many experimental efforts to measure the spatial resolution for x-ray microanalysis in the analytical electron microscope (AEM). There have been three commonly utilized specimen geometries in these experiments: 1) segregant at a grain boundary, 2) interphase boundaries oriented parallel to the electron beam, and most recently 3) spherical particles embedded at various depths in thin foils. The results of many of these experiments have been analyzed with a number of models for the broadening of the electron beam as it traverses the thin foil. These models are typically based on incoherent electron scattering, typical of Monte Carlo simulations. A vast majority of the published spatial resolution data support the incoherent scattering models as the best simulation of spatial resolution for x-ray microanalysis in the AEM. Recent experimental work using embedded particles to measure beam broadening has been used to support the coherent scattering model of beam broadening.

High current density NbTi multifilamentary superconductors have α-β microstructures tailored by thermo-mechanical processing involving interspersed cold drawing and heat treatment. A final heat treatment in the two-phase α-β field controls the volume fraction of α-Ti precipitates and subsequent cold drawing refines the scale of the microstructure to a level that optimizes flux pinning properties which affect critical current density (Jc). The volume fraction, particle size, shape and spacing of α-Ti precipitates present after the final heat treatment are important parameters of interest, and should be measurable by image analysis techniques if suitable images were available.

Al with additions of Cu is commonly used as the conductor metallizations for integrated circuits, the Cu being added since it improves resistance to electromigration failure. As linewidths decrease to submicrometer dimensions, the current density carried by the interconnect increases dramatically and the probability of electromigration failure increases. To increase the robustness of the interconnect lines to this failure mode, an understanding of the mechanism by which Cu improves resistance to electromigration is needed. A number of theories have been proposed to account for role of Cu on electromigration behavior and many of the theories are dependent of the elemental Cu distribution in the interconnect line. However, there is an incomplete understanding of the distribution of Cu within the Al interconnect as a function of thermal history. In order to understand the role of Cu in reducing electromigration failures better, it is important to characterize the Cu distribution within the microstructure of the Al-Cu metallization.

The determination of chemical composition from a ratio of the characteristic x-ray intensities (ratio technique) measured from thin specimens has become a standard technique in analytical electron microscopy. One of the main assumptions used in this technique is that the normalized distribution of characteristic x-ray intensity with mass depth (ρt), termed φ(ρt), is constant with mass depth and approaches one. If this assumption is violated, the x-ray generation must be calculated as a function of mass depth (i.e., a voltage dependence in the ionization cross section is required and the effect of fast secondary electrons must be included) and the standard absorption equation must be modified (since φ(ρt) is not constant with (ρt)). Φ(ρt) curves have been experimentally determined only for a limited number of elements because of the difficulty of performing the experiment in thin specimens. Monte Carlo electron trajectory simulations are therefore the most tractable way to calculate the depth distribution of x-ray generation.

The dynamic form factor S(q,ω) for in‐plane phonons in solid methane monolayers is evaluated at different temperatures in the self‐consistent phonon theory. The multiphonon components and interference contributions are not important in the momentum region considered and the significant broadening observed in the one‐phonon term can be contributed to anharmonic interactions in the monolayer.

The segregation of solute atoms to grain boundaries in polycrystalline solids can be responsible for embrittlement of the boundaries. Auger electron spectroscopy and analytical electron microscopy (AEM) have verified the occurrence of solute segregation to grain boundaries, however, there has been little experimental evidence concerning the distribution of the solute within the plane of the interface. Au segregation causes a change in the primary dislocation structure of small angle (001) twist boundaries in Fe. (001) twist boundaries have been produced in bicrystals of both pure Fe, and Fe containing a small amount of Au. The boundary structure characteristic of pure Fe, which is square dislocation network, changes to two different square dislocation networks, and -type, when 0.17 at% Au is added to the bicrystal and Au segregates to the boundary at its midplane. Rutherford backscattering spectroscopy was used to demonstrate that there was Au segregation to the interface, and analytical electron microscopy showed that the network was Au-rich relative to the network. The present study has clearly established that Au segregates extensively to the a dislocation cores, it remains to understand why the presence of Au has a stronger influence on the core structure and energymore » of the a rather than the a/2 dislocation, leading to the stabilization of the a dislocation network. Theoretical calculations are needed to examine the influence of solute segregation on the core energy of dislocations in Fe and Fe alloys. Work is in progress to obtain quantitative information on the amount of Au at the cores.« less

The detection and quantification of the segregation of Bi to grain boundaries in Cu using Analytical Electron Microscopy is demonstrated and the effects of time and temperature are observed. The experimental data are compared with the theoretical prediction of McLean’s segregation isotherm. Special grain boundaries are also considered. The analysis shows that the detection of the variation of segregation with time and temperature as well as grain boundary characteristics is possible using analytical electron microscopy and that the quantification techniques used here agree well with theoretical calculations of the segregant levels.