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.

A new group of ternary carbide phases which are formed by combination of an element of the scandium group (which is taken to include the rare-earth elements) with aluminum and carbon has been found. These phases are related to the series of T3BCx compounds discovered by Stadelmaier (T for a transition element and B for a B subgroup element). Atomic size effects are discussed which show that T3BCx phases behave in a manner similar to many ordered binary phases of AB3 stoichiometry. There is a readjustment in size of the various metallic components which results in effective radii compatible with cubic close packing. An anomaly which appears when the observed lattice parameters of T3BCx are related to the Goldschmidt radii of the component atoms is discussed in this light. Measurements of the intensities of X-ray diffraction peaks are used to show that the carbon atom in these phases occupies the octahedral hole in the center of a Cu3Au-type unit cell. This position is maintained in alloys which contain varying amounts of carbon.

This method for precisely determining the background level of broadened x-ray profiles assumes that the background under the peak can be approximated by a straight line, and the decay in the tails several profile widths from the peak follows a Cauchy-like law. It uses a plot of I(s)s2 vs. s2 where I(s) is the intensity and the scattering vector s = 2cosθo sin(θ-θo)/ƛ where θo is the centroid, θ the Bragg angle and X the x-ray wavelength. The true background is determined by the slope of the linear portion of the plot and its extension to s2=0 gives the rate of decay of the tails. Results on synthesized and experimental profiles show that the method is useful for Warran-Averbach analysis, because it avoids spurious oscillations and the “hook” effect in the plot of the corrected Fourier coefficients, and makes it possible to correct for overlapping tails of adjacent reflections.

A method to measure low level iodine concentrations by means of a Total Reflectance X-Ray Spectrometer (TXRF) was presented at the 1986 and 1988 Denver X-Ray Conferences (Ref. 1 and 2.). The optimum set-up of the spectrometer for this purpose was obtained by using a Cu-anode tube. The collimated beam was two times totally reflected: first on the mirror and then on the synsil sample substrate. By these means the undesired high energy bremsstrahlung was almost eliminated. This operational mode is very convenient for iodine measurement by L-lines. The detection limit of iodine was as low as 100 pg.

For simultaneous measurement of several elements (I2<Z<83) it was necessary to change the set-up of the spectrometer.

The 95% confidence linits of the x-ray elastic and stress constants of α-alumina were detemined from seven kinds of diffraction planes by the Gaussian curve method in order to investigate the diffraction plane dependence of the eonstants. No difference in the elastic constants larger than their 95% confidence intervals was observed for most diffraction planes. Also, the measured elastic constants for most planes were closer to the values calculated from the Voigt model than those from the Reuss model. Since the diffraction line of the (410) plane measured with cobalt Kα radiation by using an automated x-ray stress analyzer locates at the highest diffraction angle of 168.4, the use of this plane will allow the most accurate stress measurement. Also, the measured x-ray elastic constants for the (410) plane almost agreed with both values calculated from the Voigt and Reuss models. Therefore, the (410) plane is the most appropriate plane for x-ray stress measurement of alumina.

Without modifying the General Electric XRD-5 diffractometer accurate lattice parameters of cubic structures may be determined quite simply and precisely. The method is applicable to both solid and powder samples and gives a precision of at least ±0.00025 A. The most important step in the analysis is the alignment of the diffractometer. The specimen must be in the exact center for precise work. However, after the initial alignment, daily alignment is a routine matter. This technique for lattice-parameter determination will also be useful for determining thermal coefficients of expansion and residual-stress measurements.

Metal matrix composites develop residual strains after consolidation due to the thermal expansion mismatch between the reinforcement fiber and the matrix. X-ray and neutron diffraction measured values for the longitudinal residual stress in the matrix of three titanium MMCs are reported. For thick composites (> 6 plies) the surface stress measured by x-ray diffraction matches that determined by neutron diffraction and therefore represents the stress in the bulk region consisting of the fibers and matrix. For thin sheet composites, the surface values are lower than in the interior and increase as the outer rows of fibers are approached. While a rationale for this behavior has yet to be developed, accounting for composite thickness is important when using x-ray measured values to validate analytic and finite element calculations of the residual stress state.

Tissue's two major components: lipid and protein, are of a primary importance, related as they are to the normal life states. Assay of protein and lipid (fat and lean) in vivo is of certain criticality in human disease states, such as wasting, edema, obesity and other dyscrasias involving body mass and fat-lean balance. Since the elemental composition of lipid and protein molecules differ in a significant and regular fashion, their mass absorption coefficients differ when radiation in the x-ray and lower energy gamma ray region is used. Two monochromatic photons, one in the 20 to 30 keV region, another in the 60 to 100 keV region, can be shown to exhibit an absorption ratio in a two component system of fat and lean which provides for a determination of the component mass ratios. Photons from x-ray machines and isotopic x- and gamma ray sources have been proposed for this. The radionuclide offers qualities of stability, small size and weight, portability, zero power consumption and, generally, a certain economy. The electron capture decay of 109Cd provides a gamma ray at 88 kilovolts and a daughter (Ag) Kα doublet at 22 keV. This fortuitous energy combination is advantageous in this differential absorptiometry. The 109Cd source provides for a stable geometry and calls for the simultaneous measurement of both photons by non-dispersive x-ray spectroscopic techniques. Ten mCi of 109Cd was incorporated into a sealed source, filtered for the silver Kβ1 x-ray (at 24. 942 keV) with 0. 1 mm palladium and collimated with a grazing aperture arrangement. Fat-lean tissue simulating standard samples three cm to ten cm in length and of various component ratios were studied. Component weight percent was determined using a function of the transmitted radiation. Determinations on water (the lean simulator) and polyethylene (the fat Simulator) as well as other materials produced absorption ratios concurring favorably with the known make-up of the Simulators.

In vitro dual beam analysis of muscle tissue samples showed a high degree of correlation with the results of ether lipid extractions. Using lipid extraction values as the standard, the x-ray absorptiometric technique produced percentage lipid levels averaging within 0. 5% of the extractions.

In vivo measurements of fat content of the triceps muscle area were compared with skinfold thickness measurements of the same area. Coefficient of correlation was 0. 88.

An x-ray spectrometer has been designed for pixel by pixel analysis along lines or across selected areas of paintings and other art-objects. Characteristic technical data are: 0.8mm2 pixel size, 800mm (vert.) by 1000mm (horiz.) by 200mm (perpendicularly to object) motion distances, ±20μm precision in positioning the system, 2x3m maximum object size (mounted vertically); 2.8kW x-ray tube; Si(Li)detector. PC's are used for instrument control and new, complex data evaluation software.

A brief description of the theoretical approach of this new method is given. The main purpose of the method is to correlate in a more logical order not only the data yielding the two laws relating mass-absorption coefficient to wavelength and to atomic number, respectively, but also to delineate, within two discontinuities, the relationship existing between each value and the other ones taken as a whole. The empirical equation relating μ to λ is μ = Cλn. A table of complete values for the constant C and die power n to be assigned in the equation is given for finding the values of mass-absorption coefficients above unity for all elements (except hydrogen) and for all wavelengths between 0.17837 and 10 A. It is believed that until a complete set of experimental data obtained with modern equipment is available, this proposed method fills the enormous gaps between actual compiled values.

Knowledge of the errors in a diffraction measurement of residual strains and stresses is useful information, not only in its own right, but also because it permits automation of a measurement to an operator-specified precision. There are three sources of these errors.

X-ray fractography is a new method utilizing the X-ray diffraction technique to observe the fracture surface for the analysis of the micromechanisms and mechanics of fracture. The line broadening of X-ray diffraction profiles and the residual stress are two of the important X-ray parameters. Among them, the X-ray residual stress has been confirmed to be particularly useful for the fracture surfaces of high strength steels, and applied to the fracture surface of fracture toughness specimens and the fatigue fracture surface.

Systematic procedures are used for generating the geometrically possible close-packed ordered layers for any desired binary “ideal composition” and the various geometrically possible stacking sequences with a given number of layers of known structure. The known ordered close-packed cyrstal structure types in AB3 and AB4 alloys are characterized by the structure of the layer and by the stacking sequence. Their occurrence is reviewed in relation to pertinent variables, such as electron concentration and atomic size.

The use of quantitative x-ray diffraction (XRD) as an analytical technique has recently become increasingly popular. There ate primarily two reasons for this increasing interest in a relatively old discipline. The first is simply the need for quantitative phase analysis. This need arises from several sources such as government regulations on respiratory quartz, industrial quality control, and material research. X-ray diffraction provides a readily available technique for bulk phase analysis on chemically similiar phases. For phases which are elementally distinct, our sister science, x-ray fluorescence, can more easily provide the quantitation needed. The second reason for the increasing interest in quantitative XRD is the ready availability of automated powder diffractometers. These instruments remove much of the tedium involved in the collection and reduction of the data.

Some kinds of plastic deformation leave a residual pseudo-macrostress in the material. The existence of this stress in certain specimens introduces errors into the standard x-ray measurement of residual macrostress, namely, in specimens that have been stretched, compressed, bent, rolled, or drawn.

No error is involved in x-ray measurements on peened, ground, or machined surfaces, or in specimens where the source of the stress is remote from the surface examined.

The x-ray and magnetic evidence for pseudo-macrostress is reviewed.

Two metal foils, one pure plutonium and the other being a solid solution of 6.5 a/o gallium In plutonium, were examined, in-situ, by X-ray diffraction techniques while under pressure. The purpose was to determine the compression and compressibility of these materials as a function of pressure and to identify the products of any transformation that may occur due to the action of applied pressures.

As is well known, the fluorescent yield decreases very rapidly with the atomic number with the result, for example, that sensitive sodium and magnesium analysis is extremely difficult if not impossible with conventional X-ray spectrographs. It is demonstrated, however, that analysis for sodium and magnesium can be accomplished with sensitivity comparable to that conventionally obtained for elements such as aluminum, silicon, and phosphorous, providing that the conditions for excitation and measurement of the associated soft X-radiations are optimized, A high-intensity demountable tube using an aluminum anode has been developed which can be used interchangeably with the conventional spectrographic X-ray source. This provides a large amount of incident radiation, aluminum foil filtered, optimally close in wavelength to that of the line radiation being excited. A gypsum analyzing crystal is used along with greatly reduced beam collimation. The standard flow proportional counter and pulse height discrimination is employed. An appropriate filter, such as aluminum foil, is used as a window for the counter1 to provide further discrimination and enhanced signal-to-background ratio.

A comprehensive Fortran IV program designed to perform the matrix correction in x-ray fluorescence analysis is described. Specimens and standards can be in bulk or film form. All necessary fundamental parameters are provided by internal routines thereby requiring a minimum of input data.

While the theoretical basis for the correction of non-linearity of detector systems is well known, methods for the determination of dead-time effects must be adapted to electron probe microanalyzer systems. Two such methods, one employing both X-ray and current measurements and the other employing simultaneous X-ray measurements on two spectrometers, are described. The effect of pulse-height shrinkage at high counting rates on the linearity of the detector system is discussed. When the proposed corrections for the dead-time of X-ray detector systems employing proportional counters are applied to the X-ray intensity measurements obtained with the electron probe microanalyzer, count rates as high as 50,000 counts/sec can be used.

A so-called “Vector Method” for the texture analysis of cubic materials was presented for the first time at this conference in 1976. Since then this method has been refined and applied successfully to non cubic-materials. It is shown in this paper that the Vector Method provides several advantages over series methods of texture analysis, the most important of which being the relatively small amount of experimental data which are needed for the determination of the entire crystallite orientation distribution.