Al films have been deposited on the inside of the Color Display Tube (CDT) panel on which black matrix carbon and RGB phosphors were coated to improve brightness with the prevention of voltage down and less ion impact to phosphors. The characteristics of Al films have a close relationship with the deposition variables such as base pressure and deposition rate causing changes in Al film microstructures and differences in the reflectance. It is generally known that the reflectance is affected by the thickness, grain size, and surface roughness of the Al film: The grain size of the Al film tends to decrease when base pressure is poor due to the presence of residual gas. The reflectance of Al alloys was reported to be increased with the larger grain size.

The purpose of this study is to understand the relationship between the reflectance and the microstructures of Al films as a function of base pressure in a CDT manufacturing to optimize deposition conditions for improved reflection properties.

319 aluminum (6.5-8.5% Si, 3.0-4.0%Cu, 0.2-0.45%Mg, 0.8%max.Fe, 0.5%max.Mn) is utilized by the automobile industry for engine block and cylinder head applications. Detailed understanding of the solidification behavior is critical to optimizing the “as-cast” microstructure and the physical properties of this alloy. Samples were generated by allowing a 50 gram sample of molten alloy to partially solidify at a slow cooling rate (0.34 °C/sec). During cooling, the temperature of the alloy was monitored by a thermocouple in the center of the sample to generate a cooling curve (Fig. 1). At various locations along this cooling curve the normal cooling was interrupted by plunging the cup into an iced- brine quench. In addition to optical and SEM examination, detailed TEM analysis was performed on three quenched samples as well as one sample allowed to cool uninterrupted to room temperature. TEM sample preparation consisted of standard grinding and dimpling procedures followed by ion milling at liquid nitrogen temperature using a gun voltage of 4keV.

319 Al (7.2-7.7wt% Si, 3.3-3.7%Cu, 0.25-0.35%Mg, 0.4%max.Fe, 0.2-0.3%Mn, 0.25%max Zn, 0.25%max Ti) is utilized by the automotive industry for engine blocks and cylinder heads. Detailed understanding of the age hardening behavior of these types of alloys is important to optimize the processing of these components to yield the desired physical properties. Age hardening curves for temperatures between 100 and 305°C have been determined for a commercial grade 319 Al alloy having a dendrite arm spacing of 30(im. Samples for TEM were prepared by conventional grinding and dimpling followed by ion milling at 4keV at liquid nitrogen temperatures. The phases formed within the primary aluminum dendrites during age hardening were characterized by JEOL 2000FX and an OXFORD ISIS microanalysis system.

Age hardening curves for Al-Cu alloys are characterized by multiple hardening stages as shown by Silcock, et al. Figure 1 shows an example of a 150°C age hardening curve for 319 Al.

Optical, video and scanning electron microscopic observations show fractographic features that are used to determine the crack propagation direction and crack origin in thermally stressed single crystal sapphire hemispherical shells. These features have been typically identified in materials with symmetrically applied stresses and simple geometries. This fractographic evaluation of sapphire is unusual because of the hemispherical geometry and complex mechanical and thermal stress conditions. Computer models predict the thermal stress response of the sapphire from fast acting asymmetrical heating patterns generated during controlled laboratory testing. These experimental tests are conducted to validate the computer model predictions. When an experimental structure fails to meet the survival limits predicted by the computer model, a fractographic evaluation is conducted to determine fracture mode and to locate the crack initiation site.

Fractured pieces are examined and photographed using a low magnification, binocular optical microscope and a high resolution video camera with digitizing capabilities.

Stress corrosion cracking has been a problem in aluminum alloys exposed to an aggressive environment under high static residual tensile stress. This work is concerned with the application of electron microscopy to investigate possible causes that led to failure through stress corrosion cracking in the aluminum alloy 5182. This alloy is commonly used for making carbonated beverage containers. The containers in this study did not experience any problem at the time of the filling. However, after humid storage periods going from a few days to a few weeks, leakage at the can ends was reported in many of them. These leaks developed from a failure referred to as aluminum can end blow out.

Figure la shows an SEM micrograph of a cross section of the score imposed on the top of the can during manufacturing. The unscored metal below the score is broken when the ring or tab is pulled out during opening.

The SEM/EDS is a valuable tool in the pharmaceutical industry for aiding in the identification of isolated particles. It is a part of our systematic approach which proceeds from lower magnification techniques, e.g., stereomicroscope, to higher magnification techniques, eg., polarized light microscopy, and finally to the high magnification of SEM/EDS. Particles associated with pharmaceutical product rejects are due to a variety of sources, often due to the ubiquitous use of some materials, e.g., stainless steel alloys, in the manufacturing arena. Our particles of interest range in size from submicron to ≥ 50 μm (visible with the unaided eye), appearing in numerous shapes and/or colors. Any particles contained in a drug product or associated with the package are objectionable. Detection during production operations and/or during the terminal 100% inspection prior to market release will cause product rejection. In any case, foreign particles are not tolerated. Their identification leads to their source and thus proper corrective action.

The evolution of scanning tunneling microscopy (STM) into atomic force microscopy (AFM) have led to a family of scanning probe techniques which are widely applied in fundamental research and in industry. Visualization of the atomic- and molecular-scale structures and the possibility of modifying these structures using a sharp probe were demonstrated with the techniques on many materials. These unique capabilities initiated the further development of AFM and related methods generalized as scanning probe microscopy (SPM). The first STM experiments were performed in the clean conditions of ultra-high vacuum and on well-defined conducting or semi-conducting surfaces. These conditions restrict SPM applications to the real world that requires ambient-condition operation on the samples, many of which are insulators. AFM, which is based on the detection of forces between a tiny cantilever carrying a sharp tip and a sample surface, was introduced to satisfy these requirements. High lateral resolution and unique vertical resolution (angstrom scale) are essential AFM features.

The ability to investigate a particular feature or region of a specimen using differing kinds of analytic instrumentation can be a very valuable technique. For example, an object viewed under an optical microscope provides color, polarization, and reflectance information which is not available via SEM viewing. Similarly, the SEM with its large depth of field and ability to utilize secondary and backscattered electron contrast mechanisms, and its capability to perform compositional analysis via EDS, provides information which the optical microscope cannot. Thus, the information provided by the two instruments is complementary.

Desireable though it may be to view the same feature of a specimen via differing instruments, this is often difficult to execute in practice. The difference in contrast mechanisms which makes the excercise valuable may also make it difficult to relate the distinguishing features viewed under one instrument with those viewed in the other. Further, the issue of scale creates a large complication in many practical instances.

The ability to investigate a particular feature or region of a specimen using differing kinds of analytic instrumentation can be a very valuable technique. For example, an object viewed under an optical microscope provides color, polarization, and reflectance information which is not available via SEM viewing. Similarly, the SEM with its large depth of field and ability to utilize secondary and backscattered electron contrast mechanisms, and its capability to perform compositional analysis via EDS, provides information which the optical microscope cannot. Thus, the information provided by the two instruments is complementary.

Desireable though it may be to view the same feature of a specimen via differing instruments, this is often difficult to execute in practice. The difference in contrast mechanisms which makes the excercise valuable may also make it difficult to relate the distinguishing features viewed under one instrument with those viewed in the other. Further, the issue of scale creates a large complication in many practical instances.

Ni-base alloy welds such as EN82H weld metal are frequently employed in nuclear power applications where resistance to corrosion is required. Results of a recently reported study of the mechanical properties of EN82H welds show that this alloy is susceptible to low-temperature (∼100°C) environmental embrittlement (LTEE) in hydrogenated water. LTEE is a manifestation of hydrogen embrittlement in these alloys.1 Recent LTEE tests have demonstrated a beneficial effect of a high-temperature (∼1100°C) anneal and furnace-cool in alleviating the material's susceptibility to LTEE. Understanding the reason for the reduction in LTEE susceptibility requires detailed characterization of the microstructure so that the specific structural and compositional changes that have been induced by the solution-anneal can be identified. This study reports the results of light optical and analytical electron microscopy (AEM) characterization of the microstructures of as-fabricated and as-solution-annealed EN82H welds with the objective of providing insight into the observed LTEE behavior.

Although friction-stir welding has been developing as a viable industrial joining process over the past decade, only little attention has been given to the elucidation of associated microstructures. We have recently produced welds of copper to 6061 aluminum alloy using the technique illustrated in Fig. 1. In this process, a steel tool rod (0.6 cm diameter) or head-pin (HP) traverses the seam of 0.64 cm thick plates of copper butted against 6061-T6 aluminum at a rate (T in Fig. 1) of 1 mm/s; and rotating at a speed (R in Fig. 1) of 650 rpm (Fig. 1). A rather remarkable welding of these two materials results at temperatures measured to be around 400°C for 6061-T6 aluminum welded to itself. Consequently, the metals are stirred into one another by extreme plastic deformation which universally seems to involve dynamic recrystallization in the actual weld zone. There is no melting.

The EELS Core-Loss Atlas, like a road map, serves as an essential guide for practitioners of electron energy loss spectroscopy (EELS). Even the best maps will be incomplete, however, and one may need to plot a course by other means. Our work with materials from the nuclear fuel cycle has required new spectral lines, and even new elements, to be charted. The actinides and technetium, for instance, have important spectral features above 2 keV. The EELS technique has not often been used for detecting lines above about 2 keV because of the rapidly diminishing differential cross sections for these higher energy transitions. However, as instrumentation has progressed from scanning to parallel to CCD-array detection, statistical limitations on the high energy data have been improved by orders of magnitude. Also, in some cases, the notion of higher energy lines as “weak” is excessively pessimistic.

The binary ReSi2 and ternary (Mo,Re)Si2 alloys are of interest due to potential applications as infrared detectors [1]. Also, Re may be a beneficial alloying element to MoSi2 which is a potential high temperature structural material [2]. A recent study of the structure of ReSi2 by X-ray diffraction (XRD) revealed an orthorhombic distortion (a= 0.3121 nm, b= 0.3139 nm and c= 0.7670 nm) from the tetragonal CI lb MoSi2 structure and a Si-deficient composition of Re4Si7 [3]. Further, a weak monoclinic distortion (β=89.87°) was also inferred from high-resolution XRD [3]. In the present investigation, the orthorhombic distortion and the Si-deficient stoichiometry were confirmed by XRD and the structure of arc-melted Re4Si7 studied by transmission electron microscopy (TEM).

A bright field (BF) TEM image and the corresponding [010] zone axis selected area diffraction pattern (SADP) are shown in Fig. 1. In addition to the fundamental reflections for tetragonal Cllb MoSi2 structure,

Laves-phase intermetallics are of potential use as high-temperature structural materials. NbCr2-based C15-structured alloys are of particular interest for such applications. The effect of Ti alloying on the microstucture and mechanical properties of such alloys has been investigated and it has been shown that Ti can improve the fracture toughness of the monolithic CI 5 Laves phase8 and dual-phase (bcc and CI 5) alloys. In the Nb-Cr-Ti system, there is a complete solid solution between NbCr2 and TiCr2, with a significant range of solubility of the C15 phase and a large two phase, bcc and C15, region. The initial characterization of the defect structure of an alloy of overall composition Nb10Cr75Ti15 is discussed here.

Nb10Cr75Ti15 was prepared by arc-melting the high-purity elemental metals followed by annealing at 1400°C for 120 h and then cooling at l°C/min. Specimens were prepared for observation in the TEM by cutting 3 mm discs with a coring saw, followed by dimpling and ion milling.

Massive phase transformations exhibit a change in crystal structure without a change in composition. Nucleation and growth of this difTUsionless transformation has been studied in numerous systems including Cu-Zn, Ag-Zn and Ag-Al. There is general agreement that heterogeneous grain boundary nucleation occurs with a rational orientation relationship with at least one of the parent grains, although growth of the massive product can often occur with a partially coherent interface.

The typical Ti-48at%Al microstructure is a lamellar structure of hexagonal α2 (DO19 superlattice) and the ordered tetragonal γ phase (Ll0 with c/a = 1.01). Water or ice brine quenching of the high temperature disordered α phase results in a partial massive transformation of a into γ. Electron beam melting has been used to further suppress the equilibrium transformations. However, the current study uses rapid solidification by electromagnetic levitation and twin anvil splat quenching (cooling rates > 106 K/s) to capture earlier stages of the transformation.

Magnetic properties of permanent magnets are sensitive to their microstructure. In particular, for a class of Nd(Pr)-Fe-B magnets very different coercivity and energy products may be obtained by different processing techniques. In this work we report on the preliminary results of magnetic domains (MD) structure and grain boundaries (GB) analysis of such hot-deformed Nd(Pr)-Fe-B magnets. To reveal the fine details of MD and GB interaction the experiments were carried out by the combined use of Magnetic Foucault-Fresnel Imaging and High Resolution Microscopy.

The magnets used in this study had a nominal composition Nd13.75Fe80.25B6 (I) and Pr13.75Fe80.25B6 (II) and were produced at the General Motors Research and Development Center. Buttons of the die-upset samples were prepared from overquenched ribbons using the melt-spun technique. Thin sections were cut from the buttons obtained by die-upset of the ribbons of I and II. These sections were mechanically polished and then ion milled until perforation. Electron microscopy was done using a JEM 2000FX microscope operating at 200 kV.

Fe-13Cr stainless steel is a corrosion resistant alloy (CRA) that is widely used in oil and gas production for equipment such as tubes in wells. The high temperature, high CO2 and H2S partial pressures of typical production environments and the significant amounts of Cl- containing water that is produced along with the hydrocarbons affects the corrosion processes. Fe-13Cr is used for tubes since it exhibits passivity and low corrosion rates in production environments. But, during production operations, it is often necessary to pump strong acids into the underground rock formation through the tubes to stimulate the field and increase productivity. This is done in order to dissolve deposits that clog pores in the rock formation, thus improving permeability and facilitating the flow of hydrocarbons. This is expected to significantly degrade the passivity and lead to increased corrosion. Therefore, there is a concern about the corrosion rate during the operation and the rate at which the alloy repassivates when production is resumed.

The intermetallic, stoichiometric compound NiAl is a candidate for aggressive environments such as those encountered in aircraft engines due to its excellent oxidation resistance and high melting point. However, NiAl is limited in application by its insufficient ambient temperature ductility. This may potentially be overcome via synthesis of NiAl with a nanocrystalline microstructure. Since microstructure can also affect oxidation resistance [1], the focus of this investigation is to examine the oxidation characteristics of nanocrystalline NiAl.

Nanophased NiAl specimens were prepared by mechanical alloying followed by shock wave consolidation, which yielded consolidated material with an average grain size of 11 ±8 nm [2]. Thermogravimetric analysis (TGA) of nanosized NiAl was used to characterize the material's oxidation resistance, and performed for three different times (0.5 h, 5 h, 48 h) in compressed air at 1373 K. It was found that the thickness of the scale increased with increasing oxidation time, in accordance with parabolic oxidation kinetics.

A thorough microstructural study of common ceramics requires analysis at various length scales. Yttrium doped, polycrystalline α-Al203 was studied using a broad selection of microscopy techniques over a scale range covering seven-orders of magnitude (i.e. from mm to Å).

Yttrium doped, (1000 (Y/Al) atomic ppm) polycrystalline alumina samples were prepared by hot pressing at 1450°C at 50 MPa. Some were subsequently crept in tension. Microstructure of these samples was studied by optical microscopy, scanning electron/orientation imaging microscopy (OIM™), conventional and high resolution transmission electron microscopy. Analytical electron microscopy was performed on a VG HB501 FEG-STEM equipped with an EDS and PEELS.

On a large scale, the microstructure often consisted of bimodal sized alumina grains and second phase YAG (Y3A15012) precipitates. YAG precipitates at grain boundaries (GB) and triple points caused clusters (50μm to 1mm) of small equi-axed alumina grains (0.5-2 μm) randomly distributed over 40 area% of the sample.

Tetrahedrally co-ordinated materials can undergo stress-induced structural transformations often under invariant plane strain conditions; examples of such transformations are twinning and polytypism. The structure of a tetrahedrally co-ordinated material, XY, may be considered in terms of an assembly of “normal”, Ti’and “twinned” tetrahedra, T'I’all connected to each other at their corners. In some of these materials, e.g. SiC, GaN or CdS, these corner-sharing tetrahedra may be connected to each other in different ways, giving rise to different polytypes. In this paper, a dislocation model for polytypic transformations is discussed and a few examples of stress-induced transformations are illustrated.

In general, dislocations in XY polytypes he on basal (0001) planes and are generally dissociated into “leading’ and “trailing” partial dislocations with Burgers vectors b1 and bt’ respectively. There is also good evidence that dissociated dislocations in tetrahedrally-coordinated materials belong to the glide set and move on the slip plane in a dissociated manner.