In this work a continuous wave CO2 laser was used for melting a layer of amorphous alumina obtained by anodizing 6061 aluminum plates. Melting the surface of the anodized plates led to the formation of a new uniform corundum layer at the expense of some of the amorphous coating, resulting in a double layer coating of crysta11ine on amorphous.

The characterization of the corundum layer is essential for process optimization study. Among the non-destructive methods X-ray diffraction is useful, because it provides us with selected data on the crystalline layer.

The presence of metal oxide films from wave solder baths on timed module pins are partly responsible for non-wet problems in subsequent soldering steps. The cylindrical geometry of the pins lends itself to the characterization of thin oxide films by using the highly sensitive Debye-Scherrer camera method. As confirmed by Electron Hicroprobe Analysis (EMA), pins containing thin oxide films were used to obtain the diffraction patterns. A software program was developed that subtracts the diffraction angles of an oxids-free control pin from the pattern of the contaminated pin, and tabulates the residual d-spacing (interplanar distance) of the contaminant film.

The use of conventional θ/2θ diffraction methods for the characterization of polycrystalline thin films is not in general a satisfactory technique due to the relatively deep penetration of x-ray photons in most materials. Glancing incidence diffraction (GID) can compensate for the penetration problems inherent in the θ/2θ geometry. Parallel beam geometry has been developed in conjunction with GID to eliminate the focusing aberrations encountered when performing these types of measurements. During the past yearwe developed a parallel beam attachment which we have successfully configured to a number of systems.

The densities of sputtered thin carbon films have been determined using a novel X-ray technique. This nondestructive method involves the measurement of the transmitivity of a characteristic soft (low energy) X-ray line through the carbon film, and using the established equation I1 = I0eμpt where I1/I0 is the transmitivity, fi the photo absorption cross section, t the independently measured thickness, the density p can be easily solved for. This paper demonstrates the feasibility of using this simple technique to measure densities of carbon films as thin as 300 Å, which is of tremendous practical interest as carbon films on this order of thickness are used extensively as abrasive and corrosive barriers (overcoats) for metallic recording media disks. The dependence of the density upon film thickness for a fixed processing condition is presented, as also its dependence (for a fixed thickness) upon different processing parameters (e.g., sputtering gas pressure and target power). The trends noted in this study indicate that the sputtering gas pressure plays the most important role, changing the film density from 2.4gm/cm3 at 1 mTorr to 1.5gm/cm3 at 30 mTorr for 1000 Å thick films.

A tcchniquc for high-precision measurement of carbon thin-film thickness using X-ray fluorescence (XRF) is described. A quadratic calibration procedure is used for carbon thin films on silicon. Measurement of carbon-film thickness in a double-layer structure of carbon and CoCrX alloy is complicated by interference effects from the underlying layer. The dependence of the relative precision in measuring thickness (σT/T) on the counting time has been derived. It shows that a precision of 2% for a 25-nm carbon coating can be obtained using a W/C crystal and counting time of 4 minutes. Intensity and resolution advantages provided by the recently developed Ni/C and V/C multilayer synthetic crystals are also described.

The stress tensors were measured with x-ray diffraction in both the ferrite and cementite phases of a 1080 steel specimen deformed in uniaxial tension. The macro- and micro-stresses were separated for all the components of the stress tensors. All the components except the hydrostatic components of the micro-stresses could be determined without an accurate value of the unstressed lattice parameter. Tensile stresses were found in the cementite and compressive stresses in the ferrite along the deformation direction. The tensile stresses in the cementite were quite large.

Oscillations jn "d" vs. sin2ψ plots are due to the inhomogeneous partitioning of strains within the diffracting volume. In polycrystalline specimens, such inhomogeneity can be caused by the elastic incompatibility of neighboring grains or by the inhoniogeneous partitioning of plastic deformation within the diffracting volume. There is, however, little work on the degree of inhomogeneity required to cause a given oscillation, and the relative contribution from the elastic and plastic deformation components to a given oscillation.

The lattice misfits between γ and γ' phases in Ni-base superalloys (single crystal) were accurately determined for filings of specimens by using both a conventional X-ray tube focusing diffractometer(CXRFD) and a synchrotron-radiation parallel beam X-ray diffractometer (SRPXRD). All reflection peaks measured with the CXRFD were in a cluster of overlapping peaks because of the very small differences in the lattice parameters of both phases and the instrumental broadening due to X-ray optics including the spectral distribution of Xray source such as CuKα doublet. The deconvolution method was applied to remove the instrumental broadening from the peaks measured with the CXRFD. The window functions for the deconvolution method were calculated from CuKα doublet reflection of Si standard by a nonlinear least-square method.

The instrumental broadening of SRPXRD was much smaller than that of CXRFD since the monochromatic X-rays produced single peak profiles and constant profile shape over a wide 2θ range. A profile fitting with a pseudo-Voigt function was used to determine 2θ angles to 0.0005 deg. for the synchrotron powder data. The peak angle and shape reflected from γ' phases in γ-matrix and those fron electrochemically extracted γ'-phase were significantly different.

X-ray diffraction can be used to nondestructively measure residual stress of polycrystalline materials. In x-ray stress measurement, it is important to determine a stress constant experimentally in order to measure the stress accurately. However, every value measured by x-ray diffraction has statistical errors arising from counting statistics. The equations for calculating the standard deviations of the stress constant and elastic constants measured by x-rays are derived analytically in order to ascertain the reproducibility of the measured values. These standard deviations represent the size of the variability caused by counting statistics, and can be calculated from a single set of measurements by using these equations. These equations can apply Lu any meuhud for x-ray stress ifiesuremenL. The variances of the x-ray stress and elastic constants are expressed in terms of the linear combinations of the variances of the peak position. The confidence limits of these constants of a quenched and tempered steel specimen were determined by the Gaussian curve method. The 95% confidence limits of the stress constant were -314 ± 25 MFa/deg.

Elastic constants as a function of crystallographic direction have been measured in polycrystalline alloy samples of 17-4PH stainless steel, Ni-Cr-Fe, and Ti-6%AI-4%V using a neutron diffraction technique. The results compare best with the constant stress model of Reuss. It is demonstrated that measurements of stress can be made sampling the bulk of the material using neutrons with an accuracy comparable to more conventional x-ray methods.

Conventional methods of determination of residual stress in polycrystalline samples use either diffractometers or one-dimensional position-sensitive detectors. The most commonly used technique, the so-called "sin2ψ" method, requires several measurements at different angular positions of the sample. With diffractometers, two rotations are required, while with one-dimensional detectors, one rotation is required (except for the so-called single exposure technique, which requires two one-dimensional position-sensitive detectors). Rotation can be a potential source of errors if the sample is not aligned very carefully.

X-ray camera methods of stress measurement are inherently flexible and easy to apply in different situations because of the low weight, portability and maneuverability of the equipment. However, the digital intensity recording with the resulting objectivity and better statistical accuracy has given the diffractometer methods a distinct advantage over the conventional camera methods.

Depositing a thin layer of noble matter on a less noble material is a standard means of improving the qualities of the material. The characterization of the deposit is essential to understand tile physical phenomena involved and to improve the final product. Two physical parameters of the layer deposited are of great consequence on the behavior of the material as a whole:

1. - the crystallographic and morphological textures related or not related to those of the substratum

2. - the internal stresses.

Crystallographic texture induces an anisotropic mechanical behavior of the poly-crystal, so that the current analysis of the macro residual stress by X-ray diffraction cannot be used, because the lattice-stram distribution versus sin2(φ) presents a non-linear behavior. In order to take into accountthe influence of the texture, several authors have proposed theoretical explanations using the orientation distribution function. Many of them use the ODF to calculate the X-ray elastic constants, another one uses Bunge's texture representation to obtain analytical expressions of the strain for textured specimens.

Y.Ba2Cu3O7, a high TC superconductor powder, was shock compacted and explosively welded inside a copper matrix using the explosive fabrication methods described by Murr, Hare and Eror. The shock compression fabrication technique provides the ability to process the superconductor powders into useable structures that will minimize environmental degradation and will not negatively affect the physical or mechanical properties. Additionally, the introduction of shock induced defects are known to increase solid-state reactivity in ceramic materials. For this reason, shock compression fabrication of the superconductor/copper system offers the possibility of enhancing the superconducting properties of the YBa2Cu3O7 powders.

EPA's Air and Energy Engineering Research Laboratory is currently investigating the injection of dry calcium hydroxide [Ca(OH)2] into coal fired electric power plant burners for Che control of sulfur dioxide (S02) emissions.

Machine parts made of ceramics are usually finished by grinding. Residual stresses as well as defects introduced by grinding will influence the fracture strength and the function of ceramics parts. Although several investigations used the X-ray diffraction method to measure the grinding residual stresses, their grinding conditions were rather limited.

In the present study, sintered alumina ceramics of 99% purity were ground with a resinoid diamond wheel (#140 grain size number) under various grinding conditions. The effects of depth of cut and stock removal on the residual stress was measured with the X-ray method.

X-ray diffraction observation of the material beneath the fracture surface provides failure analysists with useful information to judge the mechanical condition of fracture.

In the present paper, stress corrosion cracking (SCC) tests were conducted by using the bluntly notched compact tension (CT) specimens of 200°C tempered AISI 4340 steel in a 3.5 NaCl solution etwixonmeat. The distribution of the residual stress beneath the fracture surface near the root of the notch was measured with the X-ray diffraction technique. The effect of the notch root radius on crack nucleation with stress corrosion was discussed on the bases of the results of X-ray observation.

The residual stress induced by grinding or some thermal treatment has a large effect on the strength of ceramics. The X-ray technique can be used to nondestructively measure the residual stress in small areas on the surface of polycrystalline materials. The X-ray stress measurement is based on. the continuum mechanics for macroscopically isotropic polycrystalline materials. In this method, the stress value is calculated selectively from strains of a particular diffraction plane in the grains which are favorably oriented for the diffraction. In general, however, the elastic constants of a single crystal depend on the plane of the lattice, since a single crystal is anisotropic, The behavior of the deformation of individual crystals in the aggregate of polycrystalline materials under applied stress has not yet been solved successfully. Therefore, the stress constant and elastic constants for a particular diffracting plane should be determined experimentally in order to determine the residual stress accurately by X-ray diffraction.

Residual strains and stresses were measured in hot-pressed α-Al2O3 composites containing 25 wt% β (cubic) SiC whiskers with and without a 50-100Å thick carbon coating. X-ray diffraction methods were used including the separation of macrostresses from the microstresses in the -Al2O3 and SiC phases by the method of Noyan and Cohen. The presence of the carbon coating on the whiskers reduced the magnitude of the residual microstresses in the whiskers by ˜13% and in the matrix by ˜10%. The measured residual stresses in the whiskers and the reduction due to the carbon film were in good agreement with calculations from recent models proposed by Hsueh, Becher and Angelini, and by Li and Bradt.