It has been suggested that the experimentally observed orientation dependence of the mobility of grain boundaries in f.c.c. metals may be related to the dependence of the rate of self diffusion in grain boundaries on the disorientation across the boundary. Later, this relative orientation effect on the rate of boundary diffusion and self diffusion was experimentally observed. It was shown by Hoffman and Turnbull that in bicrystals of silver misoricnted around (100) by 9° to 28°, self diffusion along the boundary (parallel to the common (100)) may be described in terms of a coefficient of self diffusion in individual grain boundary edge dislocation pipes, orders of magnitude larger than the coefficient of lattice self diffusion. It is significant that the coefficient of self diffusion in grain boundary dislocation pipes was found to be independent of the misorientation (i.e., of the density of edge dislocations in the boundary) at least up to 28°, suggesting that even a boundary of such a great misorientation may be considered as a network of dislocations, as far as self diffusion is concerned.

In recent experiments the relative mobilities of boundaries in various orientations between a deformed (99.98% pure) aluminum single crystal and recrystallized grains growing in it in fairly well defined, lattice orientation relationships were compared. The matrix crystal was rolled to 80% R.A. on a (110) plane in a [112] direction, after which the strip still retained its initial orientation and the texture was very sharp. Recrystallized grains quite accurately oriented so as to have highest overall boundary mobility, i.e., corresponding to 40° rotations around the two 111 axes of the matrix grain lying in the rolling plane, were produced in large numbers by random nucleation on one side of the strip (rubbing one side with sandpaper and annealing). The re crystallized grains, that were at first growing in very large numbers and quite randomly but only in the thin surface layer highly deformed by abrasion (nucleation side), on annealing for 600 sec at 350°C grew across the whole thickness (0,010″) of the rolled single crystal. As a result of very selective growth, the recrystallized grains reaching the other side of the strip (growth side) showed a very sharp texture consisting of four components with the orientations described.

A method is described which combines optical microscopy with x-ray microscopy and diffraction analysis. The topographical relationship of the grains of a fine-grained material and the fine-structural details of their surface texture are disclosed by a special technique of reflection x-ray microscopy. The experimental observations made by this technique are being correlated to those made by optical microscopy. The individual grains are subsequently analyzed for their substructure characteristics by a photographic tracer technique and a method based on the principle of the double-crystal diffractometer. Quantitaive information is obtained concerning the lattice misalignment of the grains, the size of subgrains, disorientation angle between subgrains, lattice misalignment existing within the subgrains and the nature of low-angle boundaries. Application of the method to the analysis of inclusions and precipitates dispersed in a polycrystalline matrix is discussed.

The following pages are devoted to the description of the instrument by which the method described in Part I can be implemented.

Referring to Figures 1, 2 and 3, numeral 1 designates a collimator through which the primary beam P passes, emerging from an x-ray diffraction tube (not shown). Collimator 1 is fitted with a slit system which is adjusted by adjustment screw 2, controlling thereby the divergence of the x-ray beam. The collimator support 4 is attached to the base plate 5. The height and inclination of the collimator support with respect to the base plate is adjustable, so that the instrument can be adapted to various commercial diffraction units. Locking screw 6 locks the height and locking screw 7 locks the tilt of the collimator support.

Recrystallization and grain growth of 99.998% aluminum were studied by methods combining metallographic techniques with x-ray microscopy and diffraction analysis. The recrystallked grains were shown to be the product of preferential subgrain growth whereby subgrains subtending large disoriciitation angles with respect to their neighbors exhibited the highest velocity of growth. The recrystallized grains emerging from the deformed matriv showed at first a high degree of lattice perfection, but incurred growth accidents during the growth process. Values for the mean strain-free energy of the deformed matrix surrounding the growing subgrains were obtained from the kinetics of subgrain growth.

Present knowledge of the effect of alloying on the oxidation characteristics of niobium is limited almost entirely to oxidation rate and oxygen diffusion rate data. In an effort to determine the mechanism by which alloying elements increase or decrease the oxidation rate of niobium, an x-ray study of niobium alloys was performed. Both x-ray diffraction and fluorescent studies were conducted on the base metal before and after oxidation, on the scale formed, and on the interface between the metal and the scale. From the data obtained, a definite description of the mechanism was not possible, but it appears that the Nb0 film between the metal and the Nb203 scale is the rate controlling factor. The elements Ti, Mo, Cr, W, and V which produce a substantial improvement in oxidation resistance effect the formation of a second oxide structure within the Nb0 film. All the elements which provide a measurable increase in oxidation have either a similar ionic size or a +3 valence state and in most cases have both. Elements not having a +3 valence state or similar ionic size, i.e., Cu, Mn, Si, and Zr, do not improve oxidation resistance, in fact Si and Zr act to eliminate the Nb0 film and the oxidation rate of these alloys is greater than pure niobium.

By selecting particular spectra the contrast of images may be closely controlled. Furthermore, absorption analysis of regions as small as 10 microns may be performed. Application of the absorption technique on mineral sections and the instrumental requirements for the technique are discussed.

In the course of work, on the CaO-Nb205-Si02 System, a series of compositions on the Ca0-Nb2-05 binary join has been studied. There are indications of the existence of three calcium niobates. These compounds have been characterized by X-ray powder diffraction and optical data. Single crystal studies have given information concerning the crystallography of these materials.

With the advent of nuclear engineering, x-ray diffraction has become an important analytical tool in the study of radiation damage due to neutron and gamma-ray irradiation. The materials under study in this work have rdioactive levels up to 40 R/hr. at 17 centimeters combined β and γ. The activity of the various samples under study may be due to (n, γ) reactions or fission products or both.

Data are presented to illustrate the use of sample shielding, detector shielding pulse height discrimination and the combination of all three aids in an effort to attain the most favorable peak to background ratio.

The requirement of ultrasoft x-radiation (10 to 100A) for high resolution microradiographic analysis is established. Optimum methods are described for obtaining structure, mass distribution and mass-chemical information for microscopic sample regions as small as a few square microns and for total mass as small as a few micro-micrograms. The details of the techniques and of the instrumentation which are used in high resolution microradiographic analysis are presented.

There has been a considerable amount of work reported on low magnification microradiography (up to 100 diameters) using conventional x-ray wavelengths.

Relatively little work has been done in high resolution microradiography and with ultra soft x-radiation. Nearly all which has been reported has been in application to biological research where the need for such an analysis method seems to be greatest at this time. Outstanding among this work has been that of Engstrom and his co-workers.

Much of the material which is presented in the present paper is intended as a supplement to that presented in the works of Engstrom and Lindstrom and with an emphasis upon the quantitative aspects of microradiographic analysis, using ultrasoft x-radiation.

This paper describes the use of lead shielding and pulse height discrimination as aids in reducing the background counts due to radioactive samples. The samples under study in this work have radioactive levels up to 40 R/hr. at 17 centimeters combined β + γ.

Data are presented to illustrate the tiffectiveness of shielding and pulse height discrimination individually and combined.

The electron probe is an extremely valuable tool for chemical analysis on a microscopic scale. There are many situations, however, that require analyses in the millimeter rather than micron range, where in fact, the use of the electron probe causes concern about sample homogeneity. The X-ray probe consisting of a small X-ray beam and focusing monochromator is very useful for this intermediate region. This X-ray probe is equally useful for electrically non-conducting as well as conducting specimens. Analysis need not be performed in vacuum and can be done with great rapidity.

For example by traversing a polished section of a combination of opaque minerals, it was possible to determine the distribution of copper, silver, arsenic, iron, and mercury and to show that an unidentified mineral was a copper arsenic mineral rather than an arsenoargentite as had been supposed.

X-ray fluorescence has been applied to the analysis of flotation concentrates obtained from pegmatitic uranium ores occurring in Northern Saskatchewan. It has been found necessary to use an internal standard such as strontium or yttrium. The time required for an analysis, as compared to that of conventional chemical or U.V. fluorescence methods, is considerably reduced and flotation pilot plant operations can therefore be more effectively controlled. The method has been extended to include the analysis of sulphate liquors obtained from the leaching of pegmatitic ores and their flotation concentrates. The amount of iron present in the samples is also determined by reference to the internal standard used for the uranium. This additional information is useful in assessing the efficiency of various flotation and leaching techniques.

Several instrument modifications are described including a shop-built turret mount which provides four water-cooled sample compartments, each accommodating samples up to 1.75 inches in diameter by 1.75 inches long.

Sensitivity for detection of the elements throughout the Periodic Chart is discussed for several counters.

Uranium and plutonium have been determined up to 20 w/o in metallic samples of aluminum alloys with a precision of ± one per cent in less than three minutes counting time. The determination of uranium dioxide in cryolite involved powder samples and the use of an internal standard. Uranium dioxide dispersions in bismuth metal were very heterogeneous; they were dissolved and precipitated to provide homogeneous, powders which were analyzed by measuring the intensity ratio of uranium and bismuth fluorescence.

X-ray fluorescence has been used to measure aluminum cladding thickness over plutonium alloy cores. Precision is discussed in terms of cladding thickness, aperture size, and counting time. Thickness of 11 w/o and 14 w/o plutonium-aluminum and enriched uranium-aluminum cores in reactor fuel plates has been measured by X-ray absorption in the range 0.010 to 0.030 inch with a sensitivity of ± 0.00025 inch.

The analysis of cements and ores has been studied using the Applied Research Laboratories, Inc. Production Control X-ray Quantometer (PXQ), Elements included in the program were magnesium, aluminum, silicon, phosphorus, calcium and iron. The PXQ, utilizing the polychromator concept, allows the simultaneous determination of the listed elements.

Focusing ADP, EDT, quartz and LiF crystals were used with flow Geigers or Multitrons. Helium paths were used as required. The choice of crystals, detectors, and slit widths was determined to give optimum results for each element.

The effects of briquetting and ratioing to scattered background on accuracy were studied. Various instrumental factors such as helium flow rate, detector gas flow rate, short and long term stability were also investigated.

There are various methods for handling the problem of interferences. One may me one of the weaker lines of the trace clement, but this results in considerable loss in the limit of detectability of this element. One may try pulse height discrimination techniques, but because of the linearity limitations of present day pulse height analyzers, complete elimination of the higher energy wave length is not possible. Another possible technique is to lower the kilovoltage below the excitation potential of the interfering element. This is satisfactory, but again the limit of detectability is raised for the trace element. There are many other “devices” which may be tried, but all of these involve a loss in sensitivity in the determination of the trace element.

The “novel” approach involves the use of an analyzing crystal whose second order reflection is missing due to crystal structure considerations. Germanium or silicon, cut so that (111) planes are parallel to the surface of the crystal, would be satisfactory analyzers for this purpose. The use of one of these crystals and the application of this method to the niobium-tantalum and zirconium-hafnium systems are discussed.

The wavelength of the characteristic X-radiation for the lighter elements is not constant but is a function of valence state and to a much lesser extent is a function of co-ordination number.

Commercially available X-ray fluorescence equipment is used in detecting shifts in the characteristic radiation for aluminum, sulfur, chlorine, titanium, vanadium and iron. The greatest shift is found in the case of chlorine where, using the NaCl analyzer, a shift of nearly 0.2° 2 θ is obtained in going from the Cl− in cholorides to the Cl+7 in the perchloratc. The wavelength of the Al+3Kα varies slightly as a function of co-ordination number.

Examples are given for using these phenomena in studying minerals and other compounds. The feasibility of extending the study to both heavier and lighter elements is explored.

The mutual standards concept has been applied to the X-ray fluorescence spectroscopic analysis of metcoritic Sulphide nodules for Fe, As, Co, Cr, Cu, Ni, V, and Zn. The technique is rapid and requires no addition of internal standards or binders.

On a sulphur free basis, concentrations range from 88-100% for Fe, up to 10% for Cr and Ni, up to 1% for Co, Cu and Zn, and up to 0.05% for As and V. Sensitivities vary from. 20 to 80 ppm on 100 mg. samples.

Analysis of a large number of chemically synthesized samples indicates accuracies comparable to chemical techniques employed in our laboratory.

X-ray fluorescence as a method of chemical analysis has been receiving considerable attention due to its inherent advantages of being non-destructive and generally less time consuming than conventional methods. A method of analysis is described using a pulse height analyzer in conjunction with the X-ray fluorescent unit which further extends the range of analysis.

This combination was used to measure tin in steel as low as .01% to an accuracy of .003%. Other similar analyses are suggested.