When X-ray residual stresses are determined taking into account the stress gradients within the penetration depth of X-rays, three assumptions have usually been made; 1) the stress gradient is linear in respect to the depth from the specimen surface, 2) the penetration depth of X-rays is a function of Sin2ψ and 3) the strain measured by X-rays corresponds to the average strain weighted on the intensity of the diffracted X-rays. However, the assumption of the penetration depth of X-rays is the reason we sometimes observed noticeable errors which depend on the combination of stress components in the stress tensor.

Nonlinear sin2ψ curves are often obtained in X-ray stress measurement. One of the reasons, for non-textured materials, is a steep stress gradient snowing in a surface layer of a sample. Regarding such experimental results, several new principles have been developed for X-ray stress analysis. At the present stage, we can evaluate the stress gradient in a triaxial stress state. As the next stage of the investigation, it is necessary to consider the validity of the assumptions taken in the principle, especially, the assumption about linear distribution of stress along the depth direction.

Residual stresses in an inconel alloy 600 U-bend tube, used in heat exchangers in nuclear reactors, were studied using an advanced x-ray instrument developed at The Pennsylvania State University. The work funded by the Electric Power Research Institute (EPRI) mapped both the axial and circumferential (hoop) stresses on the outside surface of the tube. The residual stresses, inherent in the fabrication of the U-bend tubes, are a major contributor to stress corrosion cracking.

Stress gradients in the direction of the surface normal influence the shape of the interplanar spacing “d” vs. sin2ψ (where ψ is the specimen tilt) plot obtained from the surface layers of a specimen.(1-3) If the gradients are caused by the shear stresses σ13, σ23, the “d” vs. sin2ψ plot exhibits “psi-splitting”, that is the “d” values measured at positive ψ tilts are different from the values measured at negative if tilts. (2) If the shear stresses σ13, σ23, are zero, but the normal stress σ33 exists in the layets penetrated by the x-ray beam, “d” vs. sin2ψ, plot exhibits curvature. (3) Various methods have been proposed to obtain the complete stress tensor from split or curved “d” vs. sin2ψ data, and all of these methods require the “unstressed” lattice spacing “d0” for their calculations.

X-ray diffraction observation of the material internal structure beneath fracture surfaces provide fracture analysists with useful information to investigate the conditions and mechanisms of fracture. X-ray fractography is a generic name given to this technique. In the present study, the residual stress on the fracture surface of the compact tension specimens for toughness tests was measured by X-ray diffraction. The effects of notch-tip radius and tempering temperature on the fracture toughness are discussed based on the results of X-ray fractography and fracture micromechanisms.

A back reflection goniometer with possibilities of Φ and Ψ rotations of the specimen was developed for stress-strain analysis in single crystals and macrograins and was completely automated. A computer software in PASCAL language was developed. The system is capable of i) optimising the Φ, Ψ and 2θ positions for a reflection, ii) scanning all the specified reflections one after another, iii) determining the lattice spacings after applying suitable corrections to the intensity data and iv) correcting the lattice spacings for temperature variations. Experimental results of measurements on an aluminum single crystal in annealed and plastically deformed conditions are presented to indicate the speed, reproducibility and accuracy of measurements. Principal sources of errors and their control in the developed system are discussed.

Sixty-five years ago Hull first described X-ray powder diffraction as a means of phase identification, and 45 years ago Hannawalt and co-workers compiled the first catalogue of powder diffraction patterns, which has evolved into a file of about 44,000 patterns (the X-ray Powder Diffraction File or PDF). The Hannawalt method of manually searching the PDF is a time-tested, effective tool in seeking a match between an unknown pattern and its correct counterpart(s) in the PDF. Recently, computerized powder diffractometers with software to perform data reduction and search the PDF have become relatively common, and these systems offer tremendous potential for rapid and accurate phase identification in simple and complex systems where the data base may include 44,000 patterns.

The JCFDS-ICDD based in Swarthmore, PA maintains and distributes a database of powder diffraction data. This database is widely used throughout the world by x-ray analytical laboratories for crystalline phase identification. It is the charter of that organization to update, expand and upgrade the quality of data in the database. As this work is carried out, the database is made available on an annual basis at a fee Commensurate with the committee's operation as a self-sustaining, non-profit organization.

High chromium white cast irons are used in the mineral processing industry as grinding balls and grinding mill liner plates. The effect of retained austenite on the field performance of these irons is not clearly understood, but it is believed that control of the retained austenite level is essential in optimizing field behavior. Improved analysis techniques are required to provide this control.

This paper presents an equal area pole figure data collection procedure for determining retained austenite in textured material in which few diffracted peaks are available for analysis. As analysis techniques improve, the significance of retained austenite in high chromium white cast irons can be better evaluated.

High alumina radioactive waste calcine is produced at the Idaho Chemical Processing Plant (ICPP) by feeding a taw liquid waste stream through a fluidized bed calcitter. Further solidification of this calcine via chemical bonding necessitates determination of the amount of crystalline phase resulting from the calcination process. X-ray powder diffraction analysis of simulated (non-radioactive) ICPP high alumina calcine shows that it consists of an amorphous phase plus three phases of varying crystal Unity; alpha, beta and gamma alumina. Subsequent quantitative x-ray analysis of the three crystalline phases was carried out using the internal standard method with sodalite as the standard phase. Limited peak selection for the alumina phases required a correction for the presence of a small sodalite peak contained within the analyzed gamma alumina peak (4° two-theta base width). Results of this study show that the calcine is composed of ∼90 weight percent gamma alumina, less than 3-4 weight percent each of alpha and beta alumina and the remaining 4-6 weight percent an amorphous component.

Thermal analysts have exploited the sensitivity of carbonate mineral decomposition to furnace atmosphere as a diagnostic tool for identifying and quantifying these minerals in mixtures and solid solutions (1-3). However, thermal analysis techniques alone cannot reveal information about the reaction products after each thermal event. In-situ high temperature x-ray diffraction is one technique that can identify these products. Using this technique, Kissinger et al. (4) identified the reaction products of the thermal decomposition of reagent grade FeCO3 (siderite) and MgCO3 (magnesite). However, the thermal behavior of analytical reagent grade carbonates differs from natural minerals (1). Milodowski and Morgan (5) used in-situ XRD to investigate the thermal behavior of the dolomite-ankerite series.

Current commercial processes for the production of wet-process phosphoric acid involve the dissolution of phosphate rock and separation of insoluble solids by filtration. Calcium is removed by the addition of H2SO4, to precipitate CaSO4·2H2O. Other metallic impurities are removed by extraction or precipitation.

In a new process. Lower grade phosphate ore can be digested with recycled phosphoric acid. If the raw acid contains a fairly high concentration of Mg, it may be enriched in fluoride ion.

The thermal expansion of ceraptic materials has become a property of interest to more people recently since the desirability of a thermally stable space platform was recognized. The interest in low thermal expansion materials in the past has been driven mildly by the recognition that low thermal expansion will foster good thermal shock resistance. The tradition of the ceramics industry for nearly one hundred years has been that zircon and cordierite were the low expanding materials. Fused silica has long been recognized for its low expansion. But when in 1947 Hummel (1957, I960) found ultra-low-expanding bodies in the lithium aluminum silicates with spodumene and later β-eucryptite structures, a new kind of phenomena had been introduced. Roy (1949), Roy, Roy and Osborn (1950) and Roy and Osborn (1959) provided much of the crystal chemical and phase diagram background on this family.

Pentaerythritol (C-(CH2OH)4) is a solid-state phase-change material which is a potential candidate for temporary storage of solar energy. This material is known to undergo an atomic structural rearrangement in the solid state above approximately 187°C, at which point a large amount of thermal energy is absorbed. Reversion of the structure to the low-temperature form releases this stored energy–thus pentaerythritol (P.E.) can be regarded as a temporary storage medium for heat.

Since the introduction of semiconductor detectors with sufficient energy resolution to resolve K-alpha X-rays from the K-beta X-rays for first row transition metals, there have been several attempts (1,2) to replace traditional detector systems (scintillation detector/graphite monochromator or proportional counter/nickel filter) in X-ray diffraction with semiconductor detectors. The goal of these experiments was to increase the total system detection efficiency by combining the K-beta discrimination and X-ray detection into a single operation. These early attempts showed that the semiconductor detector based system was more efficient, however, the problem of large dead-time losses hampered development in this area.

X-ray diffraction and electron microprobe analysis were used in combination to identify reaction phases that formed on the surfaces of low-carbon steel specimens reacted with a 75% basalt-25% bentonite mixture and anion-doped water in sealed pressure vessels at 100°C and 250°C. Reaction phases on specimen surfaces and in adhering geologic material were identified by conventional X-ray diffraction scans of entire specimens with intact reaction layers. Comparison of results from adhering geologic material and scans of selectively removed layers allowed establishment of approximate reaction gradients in the adhering packing material. Electron microprobe analysis of specimens in cross-section provided quantitative chemical analyses of adhering reaction phases, and identification of reaction layer composition gradients and thicknesses. Magnetite formed on the surface of specimens reacted at 250°C for 4 weeks. Iron-enriched clay was also observed on specimen surfaces and in the adjacent basalt-bentonite mixture. The 100°C experiments yielded surface films of a siderite-structure phase, (Fe,Ca,Mn)CO3, that were not observed in previous experiments with synthetic ground-water. Less extensive iron enrichment of the adjacent clays compared to that seen in the 250°C experiments was observed. The siderite-structure phase generally formed when no carbonate ion was present in the initial solution, implying dissolution of impurity calcite in the bentonite as the controlling factor in the reaction. The results demonstrate the utility of combining X-ray diffraction and electron microprobe analysis for characterization of reaction phases on alloys reacted with complex geologic materials.

The MAGNEQUENCH process for making high energy product (> 10 MG·Oe) permanent magnet alloys of Nd2Fe14B has been described. To advance further the commercial application of these alloys, a better understanding of the microstructure and crystallography is required.

The crystal system and unit cell parameters can be determined from the angular positions of the x-ray diffraction peaks, provided the data have been collected with a 2θ accuracy error of <0,02°. Computer based methods are available for handling the large number of calculations required. This paper describes the experimental problems encountered and solved during the determination of the cell parameters for this alloy.

Information about the conditions and reactions in a foundry cupola is essential to understand the thermochemistry of a cupola and thus improve its efficiency. A potential source of such information is coke taken from inside an operating cupola. In the region of the cupola that extends from the melt zone to the taphole, coke is directly involved in important chemical processes such as combustion, gasification, slag formation, iron sulfurization, carbon pickup, and oxide reduction. Coke is also suspected of being involved in the transport of silicon to the liquid iron. Each of these processes produces characteristic physical and/or chemical changes in the coke, making it possible to extract information about the processes from an examination of coke pieces taken from within an operating cupola. A program to study such coke samples is in progress. To effectively interpret these data it is necessary to know the temperature history of the coke being examined, especially the maximum temperature attained by the coke piece in the cupola.