Study of autoabsorption for total α and β counting

The RaMsEs Group (Radioprotection et Mesures Environnementales) of the IPHC performs research and offers services mainly in the field of radioactivity measurements and sample analysis. This report will describe some of our recent experience using a semiautomatic evaporation system to prepare large area thin deposits for total α and β counting and gives experimental and simulated results for the autoabsorption coefficients.     

Comparative determination of the α/β phase fraction in α+β-titanium alloys using X-ray diffraction and electron microscopy

A comparison is made between the measured α/β phase fractions in Ti-6246 using X-ray diffraction (XRD) and electron microscopy. Image analysis of SEM and TEM images was compared to the phase fraction estimate obtained using electron backscattered diffraction, lab and high-energy synchrotron XRD. There was a good agreement between the electron microscopic and diffraction techniques, provided that the microstructural parameters of grain size and texture are estimated correctly when using quantitative Rietveld refinement.     

Kinetics of Development by p-Phenylenediamine in Neutral and Moderately Alkaline Solutions

p-Phenylenediamine is a moderately active developer for motion-picture positive-type emulsions in neutral solution in the presence of ascorbic acid. The ascorbic acid does not act as a direct developing agent at this low pH, but prevents the accumulation of development-retarding oxidation products. p-Phenylenediamine markedly increases the rate of solution of silver bromide in a potassium bromide or a bromide-sulphite solution. Development proceeds largely by solution-physical development in the p-phenylenediamine-sulphite solutions, but direct development is important in the action of the p-phenylenediamine-ascorbic acid solutions. The two types of solutions produce silver images which differ in colour and in the morphology of the silver grains. These differences can be correlated with differences in the relative importance of solution-physical development and of direct development in the over-all process. Adsorption of the sulphite ion by the silver bromide appears to have a significant effect on the kinetics of development by p-phenylenediamine solutions which contain sulphite.     

Retransformation (α′→γ) kinetics of strain induced martensite in 304 stainless steel

Coupons of austenitic 304 stainless steel (γ) were transformed to approximately 90% martensite (α′) and 10% austenite by rolling at 77 K. Subsequently the reverse α′→γ transformation was instigated by heating the coupons to 680°C. The retransformation was monitored, in situ, by dilatometry and neutron Bragg edge diffraction (BED). Results from the two techniques show good agreement and suggest that the transformation kinetics are best described by two Avrami exponents, n=2.5 and n=0.2 respectively. A limited discussion of the lattice parameter evolution during the transformation is included. Possible mechanisms for growth dynamics and stress relaxation are discussed.     

Investigation of α platelet boundaries in a near-α titanium alloy

Transmission electron microscopy (TEM) of a bimodal near-α titanium alloy revealed the existence of retained β phase layers and silicide precipitates at the α platelet boundaries inside transformed β grains. The β to α phase transformation accompanied by the precipitation of silicide resulted in the formation of a large number of dislocations at α platelet boundaries. Orientation relationships between silicide, β phase and α phase were also identified. However high-resolution TEM (HRTEM) revealed crystal mismatches between these phases generating high strains at α platelet boundaries. The strengthening effects of the platelet boundaries are discussed in terms of dislocations slip across the boundaries. The mechanism that governs the β to α phase transformation is also discussed.     

High temperature creep of modified α + β brasses

Good machinability and formability of technical brasses α + β have to be preserved when alternative modifications are developed instead of alloying with toxic lead. Several model brasses of this type, which exhibit satisfactory machinability, are creep tested at 780 °C to compare their high temperature formability. The observed stationary creep rate and local ductility may highly differ for various alloy types. To characterize the impact of individual additions, superposition laws for the respective quantities are proposed and applied to the measured values. The strong effect of even small amounts of some additions on the creep rate and the boundary component of ductility is suggested to be due to segregation phenomenon. Rigid particles, such as phosphides, enhance significantly the creep resistance of the material, though restrict the macroscopic stability of plastic flow. On the other hand, the contribution of liquid particles to the creep damage may be effectively obstructed by phosphides.     

Calculation of efficiency functions in 4π β-γ counting

An attempt is made to calculate an efficiency function applicable to 4πβ-γ coincidence measurements as the first stage of evaluating the order of the polynomial of the fitting function. For this purpose, the β-ray energy spectra and self-absorptions of spherical particle sources are calculated by the Monte Carlo simulation under the continuous slowing down approximation. On the other hand, it is shown that three sets of absorption coefficients and partial intensity ratios corresponding to a β-ray group give analytically the self-absorption for the same particle sources. Finally, we show that the efficiency functions applicable to ⁵⁹Fe and ¹³⁴Cs are easily obtained by using the energy spectra or self-absorptions.     

Electronic Absorption Spectra of the Ce3+ Ions in Halide Melts

Reflection-absorption electronic spectroscopy was applied to measuring the electronic absorption spectra of the Ce³⁺ ions, corresponding to the 4f 5d transition, in 2CsCl-NaCl, 2CsCl-NaCl-NaF, LiF-NaF, and LiF-NaF-ZrF₄ melts. The variations in the absorption spectra of the cerium ion in these systems are due to the changes in the composition of the complex species and their symmetry. The dissolution of Ce₂O₃ in fluoride melts follows a chemical mechanism. The solubility of Ce₂O₃ in the LiF-NaF melt at 940 K was estimated.     

Machining of γ-TiAl

Knowledge of the machining parameters for titanium aluminides of the type γ-TiAl is essential for the acceptance and application of this new heat-resistant light-weight material for high performance components in automobile and aircraft engines. This work evaluates drilling, turning, sawing, milling, electroerosion, grinding, and high-pressure water-jetting of primary castings. The results indicate that there is a potential for each machining process, but a high quality of surface finish can only be achieved by some of the processes.     

Investigations of MX and γ′/γ″ precipitates in the nickel-based superalloy 718 produced by electron beam melting

Samples with a composition similar to the nickel-based superalloy Inconel alloy 718 were produced by electron beam melting of prealloyed powder and investigated with respect to type and composition of the strengthening precipitates. The matrix consists of γ grains orientated in nearly the same direction, almost like a single crystal. Coarse precipitates (<2 μm), mostly of the (Ti,Nb)(C,N,B) type with B1 structure, are aligned along the growth direction. TEM and APFIM investigations of the γ matrix revealed very fine γ″ precipitates of around 5–10 nm in size. Additionally, at small angle grain boundaries, coarser γ″ precipitates of 50–100 nm in size have been observed. The 0 01 γ//0 0 1 γ″ and {1 0 0} γ//{1 0 0} γ″ orientation relationship between γ and γ″, known from literature [M. Sundararaman, P. Mukhopadhyay, Mater. Charact. 31 (1993) 191–196], was confirmed. Some γ′ precipitates of 2–5 nm in size were observed by means of FIM.     

Inclusion Complexes of Tolnaftate with β-Cyclodextrin and Hydroxypropyl β-Cyclodextrin

Tolnaftate, an antifungal agent, was found to form inclusion complexes with both β-cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrins (HPBCDs) with two different degrees of substitution [HPBCD(A)-8% and HPBCD(B)-3%]. Complex formation in the solution state was studied using phase solubility and spectral shift methods. Solid complexes were prepared by the coprecipitation method. Solubilities and dissolution rates were determined for each solid complex, its corresponding physical mixture, and free drug. The increase in solubility of tolnaftate with added HPBCD was found to be significantly greater than with added β-CD. For both HPBCD(A) and HPBCD(B), over the concentration range 0-0.05 M. 1:1 complexes with stability constants of 1460 ± 139 M^-1 and 1860 ± 165 M^-1 were observed, respectively. Over the β-CD concentration range 0-0.02 M, a 1:1 complex with a stability constant of 1190 ± 105 M^-1 was observed. At higher HPBCD concentrations, the increase in solubility was observed to show a positive deviation from linearity (type A_p phase diagram). Using the spectral method, in a 2 5% v/v methanol in water system, the stability constants were determined to be 1020 ± 150 M^-1 1110 ± 120 M^-1 and 1100 ± 260 M^-1 for HPBCD(A), HPBCD(B) and β-CD, respectively. The solid complexes prepared showed improved dissolution over physical mixtures and free drug.     

The Dislocation Structure of a Single-Crystal γ + γ′ Two-Phase Alloy After Tensile Deformation

The dislocation structures of an industrial single-crystal γ + γ′ two-phase alloy DD3 after tensile deformation from room temperature to 1273K were studied by transmission electron microscopy. The strength of this alloy decreased with an increase in the temperature, and showed a strength peak at 1033K. At room temperature, the dislocations shearing the γ′ particles were found to be 1/3<112> partial dislocations on the dodecahedral slip system <112>{111}. Some dislocation pairs on the cubic <110>{100} system that blocked the glide of dislocations were found at a medium temperature of 873K. As a result, dislocation bands were formed. Shearing of γ′ particles by 1/3<112> partial dislocations on the dodecahedral slip system <112>{111} was also found at this temperature. At the peak temperature of 1033K, because of the strong interaction between dislocations on the {111} and {100} planes, the extent of dislocation bands with high dislocation densities was extensive. The 1/3<112> partial dislocations on the dodecahedral slip system <112>{111} also existed. When the temperature reached the high temperature of 1133K, the range of dislocation bands was limited. The γ′ particles were sheared by <110> dislocation pairs on the octagonal <110>{111} system and the cubic <110>{100} system. At 1273K, the regular hexagonal dislocation networks were formed in the γ matrix and at the γ/γ′ interface. The Burgers vectors of the network were found to be b₁ = 1/2[110], b₂ = 1/2[1–10], b₃ = [100], and the last one was formed by the reaction of b₁ + b₂ → b₃. Dislocations shearing the γ′ particles were found to be <110> dislocation pairs on the octagonal system <110>{111} and cubic slip system <110>{100} at 1273K.     

Einfluß des Gefügezustandes auf die mechanischen Eigenschaften von (α + β)- Titanlegierungen

Influence of Microstructure on Mechanical Properties of (α + β)-Ti-Alloys The amount of α- and β-phase in (α + β)-Titanium alloys for example in the alloy TiAl6 V4 may be altered to a large extend by annealing procedures. In the alloy TiAl6 V4 each temperature corresponds to a certain amount of each of these phases, the composition of which is also dependent on annealing temperature. Above about 970 °C the homogeneous β-phase appears. Additions of Iron, Oxygen, Nitrogen and Hydrogen have a great influence on the transition temperature and the distribution of the α- and β-phase. There is a great influence of the distribution of the phases on the mechanical properties. The β-phase and the α-solid solution can be quenched from high temperature and decomposed at a lower temperature, so that intermediate phases as ω from β and α₂ from α may be precipitated. The α-solid solution is anisotropic so that texturized samples have different properties in various directions. Based on these fundamental aspects it is shown to what extend these microstructures may influence the mechanical properties especially the fatigue behaviour of (α + β)-Ti-alloys.     

Amplitudenwechselversuche an der α-Kupfer-Zinnlegierung CuSn6

Cyclic Work Hardening Behavior of the α-copper tin alloy CuSn6. Polycrystalline specimens of the copper-tin alloy CuSn6 have been subjected to strain-controlled single step and two step fatigue tests. In a single step test the cyclic deformation curve at the beginning reveals strong work-hardening which is decreasing in the course of the test. A saturation of the stress amplitude is not observed. In two step tests, the material shows strong cyclic work hardening immediately after the change from low to high amplitudes, After the high amplitude is being changed into a low one, pronounced softening occurs. After changes of the strain amplitudes both these typical reactions of the material are observed up to fatigue crack initiation.