An investigation of the quasicrystalline phases obtained in alloys of Al86Mn14 under slow solidification rates is carried out. A quasicrystalline phase similar to the so-called T phase [L. Bendersky, R. J. Schaefer, F. S. Biancaniello, M. J. Boettinger, M. J. Kaufman, and D. Schechtman, Scr. Metall. 19, 909 (1985)] is found. However, this phase also shows a pseudofivefold axis and a threefold diffraction pattern similar to the same orientation in the reported phase of Al4Mn. The analysis of pseudofivefold diffraction patterns from different quasicrystalline grains shows elliptical arrangements of spots with different eccentricities. The presence of planar faults indicates the existence of slip pseudoplanes and slip directions in the quasicrystal. Different eccentricities might suggest that some of the reported quasicrystalline phases (T, T′, T″, …, etc.) are structural states obtained from the icosahedral quasicrystalline phase when particular stress environments are acting.

The sintering process at 840°C and at 925°C, of Zr-7.2 wt. % Fe was studied by room-temperature Mössbauer spectroscopy, x-ray diffractometry, and scanning electron microscopy. According to phase analysis, most of the αFe phase disappeared after 20 h of sintering at 840°C and after 4 h at 925°C. During the sintering, small quantities of the intermetallic compound ZrFe2 as an intermediate phase were observed clearly by the Mössbauer technique and very weakly by x-ray diffractometry. The relationship among the relative quantities of αFe, ZrFe2, and Zr3Fe phases was determined. The change in density as a function of sintering time was measured, and the results were explained on the basis of the different sintering stages and phase transformations.

Fluorination of YBa2Cu3O7−s at room temperature results in no change of the critical temperature but a drastic reduction of superconducting volume fraction as determined by magnetic flux exclusion measurements. Rietveld refinement of neutron powder diffraction data indicates that the bulk structure has not changed in any significant way despite the loss of superconductivity. In marked contrast, when the superconducting oxide is fluorinated at 400 °C, a structural transformation from orthorhombic to tetragonal symmetry occurs that is accompanied by essentially complete filling of eight of the nine perovskite anion sites and total loss of superconductivity above 7 K. Interpretation of neutron activation analysis and neutron diffraction results render the formula of the fluorinated product as YBa2Cu3F3.5O4.5, but fluoride ions in the unit cell were not distinguished from oxide ions.

Ion-beam mixing and thermal annealing of thin, alternating layers of Al and Nb, as well as Al and Ta, were investigated by selected area diffraction and Rutherford backscattcring. The individual layer thicknesses were adjusted to obtain the overall compositions as Al3Nb and Al3Ta. The films were ion mixed with 1 MeV Au+ ions at a dose of 1 × 1016 ions cm−2. Uniform mixing and amorphization were achieved for both Al−Nb and Al−Ta systems. Equilibrium crystalline A13Nb and Al13Ta phases were formed after annealing of ion mixed amorphous films at 400 °C for 1 h. Unmixed films, however, remained unreacted at 400 °C for 1 h. Partial reaction was observed in the unmixed film of Al–Nb at 400 °C for 6 h. After annealing at 500 °C for 1 h, a complete reaction and formation of Al3Nb and Al3Ta phases in the respective films were observed. The influence of thermodynamics on the phase formation by ion mixing and thermal annealing is discussed.

Nickel foils, 165 μm thick, have been carbon implanted at 300 K with 2, 3, and 4.2 × 1017 C ions/cm2 and implanted with a two-step implantation of 2.1 × 1017 C/cm2 at 300 K followed by 2.1 × 1017 C/cm2 at 77 K. All implantations performed at 300 K result in the formation of the metastablc phase Ni3C while the two-step implantation produces an amorphous Ni/C alloy. Surface mechanical property studies showed that both the surface hardness and wear properties are correlated with chemistry (carbon dose), and that the friction coefficient is additionally dependent on the surface microstructure. It was found that both the wear rate and coefficient of friction were reduced as the volume fracion of Ni3C increased. At the highest dose implanted 4.2 × 1017 C/cm7, the coefficient of friction was found to be lower for the sample implanted half at 300 K and half at 77 K and possessing an amorphous structure compared to the sample implanted entirely at 300 K and possessing a crystalline Ni3C structure. Increases in the surface hardness were also observed with increasing carbon content, with the greatest hardness observed in samples implanted to a total dose of 4.2 × 1017 C/cm2. The hardness at this dose was not dependent on the implant conditions or the metastable phase formed.

A quantitative thermodynamic explanation for the formation of metastable phases in the nickel-aluminum alloy system through heavy-ion irradiation is presented. The role of kinetics in the transformation to a metastable state is also investigated. Experiments involved the irradiation of both layered nickel-aluminum samples and ordered intermetallic compounds with 500 keV krypton ions over a range of temperatures and compositions. Samples were formed by alternate evaporation of layers of nickel and aluminum. A portion of these samples was subsequently annealed to form intermetallic compounds. Irradiations were performed at both room temperature and 80 K using the 2 MV ion accelerator at Argonne National Laboratory. Phase transformations were observed during both in situ irradiations in the high-voltage electron microscope at Argonne and also in subsequent electron diffraction analyses of an array of irradiated samples. Metastable phases formed included disordered crystalline structures, an amorphous structure, and a hexagonal-close-packed structure. These phase structures were modeled using the embedded atom method to compute heats of transformation ΔHs–ms from stable to metastablestates. It was found that metastable states that have moderate heats of transformation, ΔHs–ms ≍ 15%–20% of the heat of formation of the stable phase, form under irradiation. Metastable states with high heats of transformation, ΔHs–ms ≍ 50% of the heat of formation of the stable phase, do not form under irradiation. Kinetics also play an important role in determining the effect of temperature and initial structure on the formation of metastable phases.

The oxide superconductor Y–Ba–Cu–O is studied using Auger scanning microscopy. The chemical depth profiles of the samples were obtained. It is concluded that two phases are present in the sample, one corresponding to the standard composition and another that is Ba enriched. The first shows a platelet shape and the second a granular appearence that covers the surface of the sample.

The grazing x-ray reflectrometry technique was used as a way to study modifications in metallic multilayers induced by ion-beam irradiation. Due to the high sensitivity of the technique, short-range atomic displacements of an atom A in a layer B can be detected so that the first stages of ion-beam mixing can be investigated. The rate of mixing is measured and the compound A1−xBx formed at the layers' interfaces is characterized.

Excimer laser-induced sputtering of YBa2Cu3O7−x targets has been investigated. Two aspects of this process are reported here: the spectral content of the emission and sputtering of the target. Postsputtering analysis of the sputtered area of the target shows a nonstoichiometric composition: rich in Cu but depleted of Ba and Y.

Results of in situ hot-stage electron microscopic investigations on the transformation behavior of icosahedral Mg32 (Al,Zn)49 and decagonal Al–Co quasicrystalline phases are presented. It is shown that in both the cases the transformation begins with the formation of fine holes. This has been interpreted on the basis of the lower density of the quasicrystalline phase. Differences in the transformation behavior between the icosahedral and decagonal phases are highlighted.

The (0001), (1010), and (2110) faces of Bi have been pulsed laser irradiated at 0.5–0.8 J/cm2 with a Q-switched ruby laser. Nomarski interference contrast microscopy, channeling, and selective chemical etching have been used to investigate the response of the material to the laser irradiation. The response of Bi is shown to be strongly orientation dependent. The χmin and half-angle for the Bi (0001) surface have been measured and compared to theoretical values. The Bi(0001) surface has been shown to regrow epitaxially without an increase in the disorder. In contrast, the epitaxial regrowth of the Bi(1010) and Bi(2110) surfaces show a marked increase in disorder after irradiation. The levels of damage show a strong correlation to the critical resolved shear stress characteristics in the particular crystallographic orientation studied.

Changes in ac susceptibility of the high-Tc superconductor Y–Ba–Cu–O have been used to investigate the degradation of this material in the presence of high humidity. It is found that the fraction of YBa2Cu3O7 in a sample decreases exponentially with time when the sample is kept at 98% relative humidity and 20 °C. The time constant is approximately 22 days.

Systematic rapid quenching experiments on the icosahedral phase-forming system Al1 − xRux were performed for × < 20 at. %. The solidified alloys have been studied by electron microscopy and x-ray diffraction to determine their composition, constituent phases, and phase morphology. It has been determined that the icosahedral phase must form directly from the liquid and, at these quench rates, is always found in the presence of second or third phases. The results have been summarized in a metastable phase diagram appropriate for rapid solidification of Al1 − xRux at piston and anvil quench rates. This metastable phase diagram describes the results for Ru concentrations less than 14 at. %.

The alloy system Al–Li–Cu was investigated extensively over the composition range 5.8–8 Al–Cu–3Li to develop a detailed understanding of the formation and properties of the icosahedral phase, known as T2. Material from the various charges was analyzed by optical and electron microscopy, energy dispersive x-ray analysis, differential thermal analysis, and differential scanning calorimetry. The role of the melt composition and the solidification velocity were found to be crucial in determining the micro- and macrostructure and the existence of the icosahedral phase. A pseudobinary phase diagram for the region around Al6CuLi3, is presented based on these analyses. Based on this phase diagram the largest single icosahedral crystals of Al5.1CuLi3 yet reported, with diameters greater than 1 cm, were produced by Bridgman methods.

This study involved the ultrasonic measurement of the polycrystalline elastic constants of six face-centered-cubic Fe–Cr–Ni alloys, nominally Fe–19Cr–12Ni (at. %). In these alloys, Mo content ranged up to 2.4 at. %. Molybdenum lowers the Young and shear moduli, and it raises the Poisson ratio. Against expectation (because it increases volume), Mo raises the bulk modulus. Qualitatively, the results show that Ni raises the bulk modulus and Poisson ratio; but Ni lowers the Young and shear moduli. (Nickel decreases the alloy's atomic volume.) The discussion includes existing models based on 3d-electron theory.

A crystal irradiated by energetic particles is an open system capable of self-organization. The minimum requirements for self-organization of the microstructure (defect sinks) are derived by a linear stability analysis based upon a rate equation treatment of the defect reactions. The selected description eases the application also for proper chemical reactions. Coupling of defect fluxes to solute fluxes and resulting compositional self-organization in alloys is also considered

The present article first describes some characteristics of structure, chemistry, and electronic (bond) nature for grain boundaries in the A3B Li2-type intermetallic compounds. Next, the phenomenological aspects for the grain boundary brittleness of the Li2-type intermetallic compounds are reviewed with respect to the combination of the constituent atoms, the alloying effect, the stoichiometry effect, and a role of impurity or gaseous atoms. It is emphasized that the brittleness of grain boundaries in the intermetallic compounds is directly controlled by the atomistic and electronic structures at grain boundary regions. Based on these systematic investigations, it is suggested that the brittleness of the Li2-type intermetallic compounds can be manipulated by appropriate control of composition and the corresponding electrochemical bond environment at grain boundary planes and by control of test environment. Furthermore, some examples of the materials development are described.

A structural phase transition study of Ba2YCu3O6+x (x = 0 to 1) has been conducted on a series of 13 quenched samples. These samples were prepared from an orthorhombic material by annealing at temperatures from 400 to 1000 °C in air, followed by rapid quenching. All quenchings were performed by using a liquid-nitrogen-cooled copper cold well with a continuous flow of cooled helium gas. Various measurements including x-ray diffraction, thermogravimetric analysis, Meissner effect, and scanning electron microscopy were carried out in order to correlate the nature of the phase transition with erystallographic data, superconductivity, and annealing temperature. The phase transition from Ba2YCu3,O7 to Ba2YCu3O6 appears to involve two orthorhombic regions: region A with a <b ≈ c/3 below approximately 600 °C and region B with cell parameters of a < b < c/3 from & 600 to 708–720 °C. The transformation from orthorhombic to tetragonal takes place in the temperature range of 708–720 °C. This transition appears to be a second-order, order-disorder type.

A Cu47Zr53 alloy was surface processed with a directed-energy electron beam. Optical microscopy, x-ray diffraction, and transmission electron microscopy were used to identify the resolidified phases obtained under systematically varied rapid solidification conditions. The results of the investigation indicate that the underlying bulk substrate always nucleates the growth of a crystalline phase that was identified as a metastable CuZr phase with an ordered bcc (B2) structure. The maximum growth velocity of this phase was determined to be between 0.05 ± 0.02 m/s. This limit was compared under different assumptions to the predictions of a reaction rate growth theory. As the solidification speed increased beyond this limit, the crystalline growth eventually ceased and glass formation occurred in the remaining undercooled liquid under rapid cooling conditions. Crystalline particles also nucleated and grew in the liquid at intermediate cooling rates. These particles had a dendritic morphology and were also a CuZr phase with the B 2 structure.

After a short review on temperature dependence of the intrinsic coercivity in sintered Nd–Fe–B-type magnets is given, recent experimental results concerning the coercivity-anisotropy (HC–HA) correlation in B-rich Pr–Fe–B and Nd–Fe–B sintered magnets and the influence of the surface conditions of the sintered Nd–Fe–B magnets on the coercivity are reported. The results are interpreted in terms of the μoHc vs cμoHA – NIs plot, where Is is the spontaneous magnetization of R2Fe14B (R = Pr or Nd) and N is the effective demagnetization field coefficient.