An important feature of polycrystalline materials is the orientation distribution of crystallites also known as crystallographic preferred orientation or texture [1]. Conventionally it is measured by x-ray diffraction, averaging over sample surfaces. With demands for more quantitative material characterization, both in engineering and earth sciences, new methods have been developed. Two dimensions are of interest: Averages over larger sample volumes give a better representation to estimate bulk physical properties. Here neutron diffraction is advantageous. Because of minimal absorption large sample volumes (1-50 cm3), rather than surfaces can be analyzed [2]. If textures are locally heterogeneous, it may be of importance to analyze small regions. With a synchrotron microfocus beam volumes as small as 5 μm3 can be characterized [3]. These methods have been quantified and are extensively applied in metallurgy and geology. They provide good statistics for appropriate sample grain size but they analyze bulk textures and contain no information on local orientation correlations. Furthermore, for geological samples with low crystal symmetry, the diffraction patterns are often very complex with many overlapping peaks, making identification difficult. In such cases orientation imaging, using electron backscattered diffraction patterns (EBSD) in the SEM is useful [4]. Though grain statistics are generally much inferior, new information can be gained.

Measurement of the geometry of triple junctions between grain boundaries in polycrystalline materials is used to generate large sets of dihedral angles from which maps of the grain boundary energy are extracted. A preliminary analysis has been performed for samples of magnesia and aluminum based on a three-parameter description of grain boundaries. An extended form of orientation imaging microscopy (OIM) was used to measure both triple junction geometry via image analysis in the SEM and local grain orientation via electron back scatter diffraction. Serial sectioning with registry of both in-plane images and successive sections characterizes triple junction tangents from which true dihedral angles are calculated. If there is local equilibrium at each triple junction, we may apply Herring's relation. By limiting grain boundary character to a (three parameter) specification of misorientation for the preliminary analysis, we can neglect the torque terms and apply the sine law to the three boundaries. This provides two independent relations per triple junction between grain boundary energies and dihedral angles. By discretizing the misorientation and employing multiscale statistical analysis on large data sets, (relative) grain boundary energy as a function of boundary character can be extracted from triple junction geometry. The results are discussed with respect to current understanding of grain boundary structure based on their crystallography. The results suggest that a three parameter characterization of grain boundaries (lattice disorientation) is not an adequate description of boundary character. A full analysis including torque terms and a five parameter boundary description is under development.

During plastic deformation of typical metals the original grains subdivide. Subdivision by cell formation is a well-known phenomena in metals with medium to high stacking fault energy, but the subdivision may also take place on larger length scales by: i) Formation of single-walled dense dislocation walls (DDWs) and/or double-walled microbands (MBs). The DDWs/MBs are seen as elongated, nearly straight, vertically parallel dislocation boundaries which delineate several cells, thus bounding cell blocks. Typical examples are shown in Fig. 1. ii) Subdivision on a grain scale, for example due to grain-grain interactions or due to the formation of transition bands separating matrix bands. This subdivision is typical for both single crystals and polycrystals. For a general description and recent overview, see [1, 2].

The grain subdivision depends on the orientation of the grains. The morphology may appear different in grains of different orientations and the DDW/MBs can be parallel or inclined to a slip plane.

Deformation and thermal processing operations can produce structurally heterogeneous and anisotropic alloys. Thick, hot-rolled aluminum plate is an excellent example of such a material. Due to the plate size and thermomechanical conditions experienced by the plate during processing, significant gradients in material structure arise. These gradients are especially strong in the through-thickness or normal direction (ND) of the plate. In AA 7050, an aluminum alloy developed for thick plate applications, gradients in microporosity, grain morphology and crystallographic texture are known to exist. These features have been linked to material properties and performance measures in this alloy. Recent advances in high speed machining technology have made it possible to consider thick AA 7050 plate for an increasingly large number of airframe components. Because of its inherent heterogeneity, however, designing flight-critical components machined from AA 7050 plate will require one to quantify and mathematically represent the variation of the relevant microstructural gradients.

This work describes the investigation of plastic strain in tensile deformed polycrystalline copper using the automated Electron BackScatter Pattern (EBSP) technique of electron diffraction in the Scanning Electron Microscope (SEM). A strong correlation was found between the known accumulated plastic strain in OFHC copper tensile specimens and quantitative measurements of intra-grain misorientation obtained from an analysis of automated-EBSP data.

Previous works on strain measurement using EBSP analysis have focused on the influence of dislocation density on the intensity profiles of diffraction bands. It is known that for some materials, like copper, deformation strain produces highly organized dislocation structures and thus the dislocation density is very inhomogeneous on the sub-micron scale probed by EBSP. This suggests that plastic strain analysis using the EBSP dislocation density analysis route will be difficult to reliably implement in these materials.

Bainitic low alloy steel has a complex microstructure exhibiting several types of boundaries. The boundaries in bainitic steel, although certain boundaries are absent with respect to the alloy composition and the manufacturing process, could be typically divided into 4 types; dislocation cell boundary, lath boundary, packet boundary, and prior austenite grain boundary, in increasing order of size. The size and distribution of the respective boundaries are an important factor which controls the mechanical properties of the steels, including brittle fracture. In the present research, the characteristics of the boundaries in the bainitic low alloy steels were investigated in view of misorientation between grains enclosed by the respective boundaries.

The alloys investigated were Mn-Mo-Ni low alloy forging steels having chemical compositions shown in TABLE 1. Steel-A was manufactured by the Vacuum Carbon Deoxidation(VCD) process. For the finer prior austenite grain size, Steel-B was produced by the aluminium addition and the silicon killing process. Before EBSD analysis, the microstructures of the alloys were observed using SEM and TEM. EBSD measurements were obtained using a Link OPAL system(Oxford) linked to a JEOL JSM 6300 SEM operating at 15KeV with the sample tilted at 70°.

A standard commercial EBSD system, comprising a CCD camera (Nordif) and acquisition software (HKL Technology) has been interfaced to a Philips XL30 FEGSEM, and the spatial and angular resolutions for EBSD compared with a conventional W-filament JEOL 6300 SEM equipped with a similar EBSD system.

In characterising a grain or subgrain structure, overlapping diffraction patterns are obtained at the boundaries, and the effective spatial resolution can be defined as the distance over which the patterns cannot be solved. The spatial resolution is best in the direction parallel to the specimen tilt axis (LA), typically some three times better than for the direction perpendicular to the axis. The resolution is conveniently determined by measuring the fraction of patterns which are solved (Ns) during a raster scan of the sample. For a microstructure of equiaxed grains of size D, LA is given approximately by D(1-Ns)/4. Figure 1 is a plot of Ns against D−1 for aluminium samples under optimum operating conditions, and it is seen that the spatial resolution in the FEGSEM is some three times better than in the W-filament SEM.

The effect of beam current on LA is shown in figure 2. For the W-filament SEM, LA is a strong function of the probe current.

Automated Crystal Orientation Measurement/Mapping (ACOM) as used in the SEM by unattended interpretation of Backscatter Kikuchi Patterns from bulk surfaces (BKP)* has become an invaluable new technique for the quantitative characterization of microstructure on a grain-specific level. The principal objectives are to relate grain orientations and misorientations directly to grain location in the specimen surface, to determine the character of misorientations and grain/phase boundary planes, and to calculate derived entities such as microtexture and anisotropic local materials properties. These quantities are commonly depicted in pseudo-colors on the scanning grid to form Crystal Orientation Maps (COM) or similar “images” of the microstructure. Stereological as well as orientation related data, as most sensitive indicators of the production process and use of a material, are readily available for basic research and quality control. The three-dimensional representation of microstructure by consecutive sectioning is still a challenge to enable the study of inhomogeneity beneath the surface and the three-dimensional connectivity of multiphase material. Dynamic experiments are a further promising application of this new technique in the SEM.

Electron Back-Scatter Diffraction (EBSD) is a technique used for obtaining microtextural information from bulk samples in the scanning electron microscope (SEM). number of good commercial systems provide hardware and software to acquire and analyze the electron back scatter patterns (EBSP). The systems come with tools to visualize crystal orientation, and map grain and grain boundaries. However money is always in short supply, and for studies which do not require mapping, we have found it more economical to build our own EBSP system using readily available off-the-shelf components.

An EBSP's are formed by the intersection of the diffracted back scattered electrons with a phosphor screen placed in their path. We acquire this pattern by viewing the phosphor.screen through a view port with a CCD video camera which is configured for on-chip integration. On-chip integration allows the signal to be amplified without extensive electronic noise. We made a port cover for the right-hand port of the DSM-962 SEM on which a 2” diameter view window is fitted.

This paper describes a new form of orientation imaging microscopy: Adaptive Orientation Imaging Microscopy or AOIM. In standard OIM experiments the local orientation of the crystal lattice is determined with respect to a suitable reference frame by acquiring and indexing electron back-scattering (EBS) patterns on a square or hexagonal grid of sampling points. Since its invention, OIM has been extensively used to characterize polycrystalline materials. With the fast development of computers and CCD camera systems in the past few years, the standard OIM can now acquire and index of the order of 4000 EBS patterns per hour.

In a typical OIM experiment one is usually interested in either the overall texture of. the sample, or in the types and relative frequencies of grain boundaries. In the former case the proper way of acquiring orientation data involves the use of an equidistant grid of sampling points. In the latter case, however, a large fraction of the acquisition time is wasted sampling the grain interior, which does not provide any information about the grain boundaries.

This work discusses using the automated Electron BackScatter Pattern (EBSP) technique of electron diffraction in the Scanning Electron Microscope (SEM) for measuring grain size in polycrystalline materials. A quantitative analysis of 2-D grain size from a standard metallographic section can be made in less than one hour using an automated-EBSP system on a traditional SEM and dedicated analysis software. Thus, the automated EBSP technique provides a useful and cost-effective way to determine grain size. A common measure used to describe grain size is mean intercept length (MIL) and the present discussion will be limited to determining MIL using EBSP.

Grain size analysis using optical microscopy is strongly influenced by sample preparation, which involves etching of the polished section to reveal boundaries. Boundaries that are to be avoided in determining MIL, such as sub-grain boundaries and twin boundaries, may be revealed and mistaken for random high angle boundaries.

Recent advances in cameras and computers have made it possible to build electron backscattering pattern (EBSP) cameras which can give crystallographic information from diffraction patterns in the scanning electron microscope (SEM) on a routine basis.[1] There are a few hundred such systems world wide and the number is growing fast. In the case of crystalline samples (nearly all applications of SEM outside the biomedical field), it will surely soon be considered essential to fit an SEM with an EBSP system, just as it is now considered essential to have the SEM equipped with an energy-dispersive x-ray spectroscopy (EDS) system. There are at least four commercial manufacturers of EBSP systems. In the next few years, then, I anticipate that many owners of existing SEMs as well as buyers of new instruments will be faced with the problem of selecting an EBSP system. This paper presents some of the issues involved in making such a choice.

As in many technical decisions, different people will have different needs and put different priorities on the specifications to be met. An instrument which is to be used to do repeated analyses of aluminum for beer cans will have different needs from a system used mostly to teach crystallography, and those will be different in turn from the needs of a system used to determine which phases are present in geological samples.

This work describes an investigation of the microstructure of a γ/γ' Ni-base superalloy using the automated Electron BackScattering Pattern (EBSP) technique with simultaneous energy dispersive x-ray spectrometry (EDS). The goal of the investigation was to determine if EDS measurements necessary to discriminate γ' from γ' could be obtained when acquired simultaneously with a normal, high speed automated EBSP scan. The acquisition conditions that impact the EDS collection are: surface tilted ∼70 degrees from the beam axis, 70mm spectrometer to specimen distance limited by interference from the EBSP detector and approximately 300 ms available acquisition time.

Thermo-mechanical processing of superalloys can produce coarse γ' that appears both within grains and at grain boundaries. In some conditions, the coarse γ' may be as large as many γ grains. As the crystal structure of γ and γ' are very similar, it is not possible to discriminate between the two phases using typical EBSP analysis. However, one needs to discriminate these phases in order to measure properties of the γ matrix such as texture and grain size.

Metals on oxide systems are important in applications such as catalysts and gas sensors. The Au/ TiO2 system is of particular interest because of its high activity for low temperature oxidation of CO and its good sensitivity as CO gas sensor. In this study, we are reporting results on the effect of substrate temperature on epitaxial orientation relationship of Au particles formed on TiO2 (110).

Two Au films were grown on TiO2 (110) substrates by vapor deposition in a UHV chamber. The first one was produced by evaporation of a 12nm thick Au film at 300K, followed by annealing at 775K for 1 hour. The second one was produced by direct deposition of a 12nm film on TiO2 substrate maintained at 775K. The samples were transferred in air to the Field Emission Scanning Electron microscope (LEO 982 Gemini) for imaging and diffraction. .Electron Backscatter Diffraction (EBSD) patterns were taken from individual Au particles using the Opal system (Oxford Instruments). With this system, a spatial resolution of the order of 80 nm has been achieve for Au.

A typical HRSEM image of the Au film deposited a 300K and annealed at 775K is shown in Fig. 1 revealing a discontinuous Au film consisting of discrete Au particles in the range from 20 to 150 nm.

Crystallographic structure plays an important role in determining the fundamental physical properties of metallic thin films and superlattices, and structural characterization of such films is crucial for furthering the application of these materials [1]. Epitaxial films are usually characterized using a wide range of techniques including x-ray diffraction, REED, neutron diffraction, and highresolution electron microscopy. A complementary approach is electron backscatter patterns (EBSP), which is an SEM technique that can be used to measure crystallographic orientations of single or polycrystals [2].

In this work, EBSPs have been used to characterize the crystallite size and orientation of sputterdeposited Cu films. The EBSPs were formed in a CamScan 44FE SEM and recorded using an ORTEX CCD camera system. The images were analyzed using the Channel+ software package, and orientation maps were plotted using Channel+Ice [3].

Directionally solidified (DS) in-situ composites based on (Nb) and (Nb) silicides, such as Nb5Si3 and Nb3Si, are presently under investigation as high-temperature structural materials [1, 2]. Alloying additions of elements such as Hf, Ti and Mo to these silicides are also being explored. The present paper describes the microstructure of a DS Nb-silicide based composite before and after creep deformation.

Alloys were prepared from high purity elements (>99.9%) using induction levitation melting in a segmented water-cooled copper crucible. The alloys were directionally solidified using the Czochralski method [2]. Creep tests were conducted at 1200°C to 50% deformation. Characterization was performed using scanning electron microscopy, electron microprobe analysis (EMPA), and electron backscatter diffraction pattern analysis (EBSP).

Using the new method known as Orientation Imaging Microscopy (OIM), characterization of mesoscale aspect of the internal structure of polycrystalline materials in the two-dimensional section plane has become routine. However, in some applications which primarily focus either on the characterization of interface types or on their connectivity, OIM is rather inefficient since only the scan points that lie adjacent to the interfaces are used to determine interface character. When the OIM grid spacing is dictated by the precision with which the interfacial in-plane inclination must be determined in the section plane, the efficiency with which conventional OIM can harvest interfacial data is rather poor.

In this paper a new approach and system of microscopy is described, called the Mesoscale Interface Mapping System (MIMS). MIMS overcomes the challenges associated with OIM by directing the beam to the vicinity of interfaces which have been identified by a microstructural contrast image.

Electron diffraction was observed in 1928 by Kikuchi. In electron diffraction, diagrams characteristic of the crystal lattice and the phase orientation are formed. Consequently, Venable, then Dingley recently developed electronic diffraction coupled with scanning electron microscopy. Their approach enables micrometric scale examination of a specimen obtained by simple metallographical preparation (polished surface). Since the 1980’s, this technique has benefited from strong technological and computerized development which have led to the sale of the first systems under the name of Electron Backscatter Diffraction (EBSD). Niobium is used in the cast industry of uranium to refine it (getter function). The strong affinity of niobium for carbon leads indeed to the formation of small precipitates of niobium carbides. Whereas carbon cannot be detected by EDS because of its high absorption by the niobium (absorption coefficient μ=29000), hardness measurement indicates the presence of carbides (HV30 = 2000), but without further information on the nature of those carbides.

We report here our preliminary results on orientation determination and phase identification using the electron backscatter diffraction (EBSD) technique. Using a scanning electron microscope (SEM) equipped with the EBSD attachment. it is now possible to study the correspondence and orientation relationships of parent-phase and martensite variants in shape memory alloys (SMAs). Previously, such an information was obtained from large single crystals studied by micro-beam X-ray Laue diffraction and supplemented by transmission electron microscopy study of thin foils. Figs. 1(a), (b) and (c) are three EBSD patterns taken from neighboring areas in a Cu-12.55Al-4.86Ni (wt%) SMA. Computer simulation reveals that Fig. 1(a) belongs to the parent-phase of D03-structure type, and Figs. 1(b) and (c) belong to variants A and D of 2H martensite, respectively. Corresponding simulated EBSD patterns are shown in Figs. 1(d), (e) and (f). Fig. 1 indicates that the (0 0 2)A basal plane of the martensite variant A is transformed from the (-2-2 0)p plane of the parent-phase and its [0-1 0]A direction from the [0 0 1]P direction. The (0 0 2)D basal plane of the martensite variant D is transformed from the (2-2 0)P plane of the parent-phase and its [0 1 0 ]D direction from the [0 0 1]P direction.

A relationship between the local microstructure (crystallographic orientation) of a sample and an image from a scanning electron microscope (SEM) has been an elusive goal. Being able to show the structure from an exact area and relate it to other data is essential to the understanding of the structure relationship to the entire sample. Conventionally microtextural information of tapes is obtained by using x-ray diffraction and pole figures. But this only provides information about the global texture. The precise location is not well defined. The ability to physically transfer the sample from the x-ray diffractometer to a SEM and accurately state that this is the same area has been impossible. Electron Backscatter Diffraction Patterns (EBSPs) have been obtained in an electron microscope and the exact area in relation to the rest of the sample is determined. Thus larger areas can be defined and put together to form a composite of an entire sample. This, however, may be hard to accomplish in that defined areas for the image scan may be at a different scale than the EBSP scan. A contrast method of imaging in the ESEM using an increased vacuum and the ESD yields a good correlation to mapped areas obtained from EBSPs or also known as backscatter electron Kikuchi diffraction patterns (BEKPs or BKPs).