Pb-Bi Alloys Research Articles

High Temperature Corrosion of Steels in Liquid Pb-Bi Alloy

High Temperature Corrosion of Steels in Liquid Pb-Bi Alloy

Diffusion kinetics of Bi and Pb–Bi monolayer precursing films on Cu(1 1 1)

We have used Auger electron spectroscopy to study the diffusive spreading and adsorption of pure Bi and Pb–11 at.%Bi precursing films on Cu(111) surfaces, from droplets of the respective materials. The Bi diffusion coefficient (DBi) increases with Bi-coverage. However, in the intermediate coverage range, DBi remains approximately constant, which is presumably due to the formation of an ordered Bi hexagonal overlayer. In the case of Pb–Bi alloy spreading, the presence of Bi slows down the Pb diffusion kinetics significantly. The kinetics of Bi spreading are also slower in the presence of Pb, but the effect is less marked. The equilibrium concentrations both at the Pb–Bi drop surface, and in the surrounding precursing film, were found to be Bi-enriched.

Diffusion kinetics of Bi and Pb?Bi monolayer precursing films on Cu(111)

We have used Auger electron spectroscopy to study the diffusive spreading and adsorption of pure Bi and Pb–11 at.%Bi precursing films on Cu(1 1 1) surfaces, from droplets of the respective materials. The Bi diffusion coefficient ( D Bi ) increases with Bi-coverage. However, in the intermediate coverage range, D Bi remains approximately constant, which is presumably due to the formation of an ordered Bi hexagonal overlayer. In the case of Pb–Bi alloy spreading, the presence of Bi slows down the Pb diffusion kinetics significantly. The kinetics of Bi spreading are also slower in the presence of Pb, but the effect is less marked. The equilibrium concentrations both at the Pb–Bi drop surface, and in the surrounding precursing film, were found to be Bi-enriched.

Solid-liquid equilibria in nanoparticles of Pb-Bi alloys

The melting behavior of isolated nanoparticles of Pb-Bi alloys was observed by hot stage transmission electron microscopy. Dark-field images acquired as a function of temperature permitted the melting behavior of individual nanoparticles to be characterized as a function of their composition and size. In this way, the experimental measurements could be used to find the temperature at which the onset of melting occurred and the temperature at which the transition from a liquid-solid two-phase particle to a complete liquid particle occurred. From these data, phase diagrams of individual, isolated nanoparticles were constructed as a function of the size of the nanoparticle. Several deviations from the melting behavior of bulk materials were observed. For particles of a given composition the melting temperature is lowered relative to the melting temperature of bulk material and the depression of temperature increases with the inverse of the particle radius. The liquid and solid phases follow melting paths that form liquidus and solidus bands on the temperature-composition phase diagram. The range of two-phase coexistence shrinks as the solute concentration decreases, and the liquidus and solidus bands finally coalesce into a single line at low solute concentrations in apparent violation of the Gibbs phase rule. Of particular interest is the observation that melting begins and ends abruptly as temperature is increased. Considering the isolated particle as a thermodynamic system in contact with a heat reservoir and a pressure reservoir, the conditions for two-phase equilibrium in the particles were calculated from the total internal energy of the particle and the reservoirs. The loci of parameters of the calculated minimum points of the total energy were compiled to calculate a phase diagram for alloy nanoparticles as a function of their size. This calculated diagram contains all of the special features observed experimentally and agrees quantitatively with the experimental measurements. These features should be sufficiently general to apply to other alloys. The quantitative conformance of the experimental with the calculated results is sensitive to the material properties, in particular to the composition dependence of the surface energy of the liquid.

Behavior of the resistivity of metal alloys during collective recrystallization

The kinetics of collective recrystallization in Sn-Pb, Sn-In, Sn-Zn, Pb-Sn, Pb-Bi, and Pb-In alloys have been studied using the conductivity method at T = 180°C.

The Surface Tension of Liquid Near-Eutectic Alloys of Lead–Bismuth System

The method of large (sessile) drop is used to measure the surface tension (ST) of seven molten lead–bismuth alloys containing 33.3, 38.1, 44.5, 50.8, 64.6, 70.4, and 74.0 wt % bismuth in the temperature range of 473–646 K. The Pb–Bi alloys to be investigated are prepared by the gravimetric method. The purity of starting lead and bismuth is no lower than 99.99 wt % for each of these metals. The confidence error of the measurements does not exceed 1%. The experimental results are compared with the data of other authors on the ST of the liquid alloys of the Pb–Bi system.

Dislocation induced line-broadening in cold-worked Pb-Bi binary alloy system in the α-phase using X-ray powder profile analysis

An X-ray diffraction line profile analysis on cold-worked Pb-Bi alloys in the α- phase is presented. The anisotropic broadening of X-ray diffraction lines has been interpreted in terms of dislocation induced strain broadening only. Dislocations are found to be predominantly of screw type from a modified Williamson–Hall analysis. Due to the almost symmetric shape of the X-ray line profiles, a restrictedly random dislocation distribution was assumed in the modified Warren–Averbach analysis. The dislocation densities are of the order of 10 11 cm −2 and decrease for annealed specimen. The dislocation arrangement parameter ( μ) decreases from more than 1.0 for cold-worked samples to less than 1.0 for annealed samples. This indicates a rather short ranged strain fields in annealed samples compared to cold-worked samples. Relative change in the dislocation arrangement parameter increases with solute concentration.

Surface tension and wetting behaviour of molten Bi–Pb alloys

The present work represents an experimentally based investigation on the surface properties of molten Bi, Pb and Bi–Pb alloys. The surface tensions of the two pure elements and of seven alloys were measured by the sessile-drop method over the temperature range 623–773 K. In addition the wetting behaviour of the eutectic Bi–Pb alloy on AISI 316L substrate was also investigated in the same temperature range. The results obtained show general agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values obtained by the application of the compound formation model (CFM).

Tensile testing of MANET II in flowing Pb–Bi alloy at elevated temperature

Experiments were carried out to study the influence of lead bismuth eutectic (LBE) on the tensile properties of the martensitic CrNiMoVNb steel named MANET II (Martensit for Next European Torus) considered as structural material for the first wall and blanket in fusion reactor conceptual design. In order to investigate a possible liquid metal embrittlement (LME) effect, tensile tests in flowing Pb–Bi at various temperatures (between 180 and 300 °C) were carried out. For comparison of the tensile test results achieved in Pb–Bi, tests were also carried out in the same facility but in an Ar atmosphere at the same temperature. After the tests, the fracture faces of the specimens were examined by SEM to analyse the fracture type (brittle or ductile). Additionally the ruptured specimens were longitudinally sectioned and analysed by metallurgical and SEM examinations.

Surface properties of Bi–Pb liquid alloys

The present work represents an experimentally based investigation of the applicability of a statistical mechanical theory in conjunction with a compound formation model (CFM) to describe surface properties of Bi–Pb liquid alloys. The surface tension of molten Pb, Bi and Bi–Pb alloys has been measured by the sessile-drop method over a temperature range. The results obtained show general agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values. Based on the phase diagram evidence about the existence of the ε-Pb 3Bi intermetallic compound, the phenomenon of compound formation in Bi–Pb liquid alloys has been analysed through the study of surface properties (surface tension and surface composition) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the frame of CFM.

A model for the prediction of the corrosion of steels in flowing liquid lead alloys

The values of the solubility and diffusion coefficients of iron in the eutectic liquid alloy Pb–17Li to be used in a corrosion model of Balbaud-Célérier and Barbier should be taken from the corrosion data of Borgstedt and Röhrig. These data are consistent with the Einstein–Sutherland equation and values for diffusion coefficients of metal atoms in liquid metal solutes. They are lose to those in pure lead or in the eutectic Pb–Bi alloy, and the model generates correction corrosion rates with their application.

Corrosion studies in liquid Pb–Bi alloy at JAERI: R & D program and first experimental results

The program of corrosion study in liquid Pb–Bi at Japan Atomic Energy Research Institute (JAERI) is described. It was planned to clarify effects of parameters such as temperature, temperature difference between high-temperature and low-temperature parts, oxygen concentration in liquid Pb–Bi, flow rate, irradiation, stress and chemical composition of materials. The program contains the basic corrosion study in static Pb–Bi for elucidation of corrosion mechanism and effects of oxygen concentration in liquid Pb–Bi and ion irradiation on corrosion behavior. It also contains the corrosion study in flowing Pb–Bi using a corrosion testing loop. From the initial result of the static corrosion tests in oxygen saturated Pb–Bi at 550 ° C for 500 h, it was shown that the thickness of the corrosion film decreases with increasing Cr content in steels.

A molecular dynamics study of lead-bismuth-silicate glasses

We present the results of molecular dynamics (MD) simulations of the structure of ternary lead-bismuth-silicate glasses of compositions xPbO(0.3-x)Bi/sub 1.5/0.7SiO/sub 2/, x=0.06, 0.15, 0.24, and their totally reduced forms, i.e. xPb(0.3-x)Bi0.7SiO/sub 2/, x=0.06, 0.15, 0.24 systems. The simulations have been performed in the microcanonical (NVE) ensemble, using two-body interaction potentials. The results can be summarized as follows. With increasing PbO content in unreduced xPbO(0.3-x)Bi/sub 1.5/0.7SiO/sub 2/ glasses, the Pb-O and Bi-O first pair distribution function (PDF) peaks become sharper, and the fraction of strained 2 and 3 member Si-O-Si-O- rings decreases significantly. In the case of reduced xPb(0.3-x)Bi0.7SiO/sub 2/ glasses, similarly as in reduced binary lead-silicate and bismuth-silicate glasses, a strong tendency to agglomeration of neutral atoms occurs. The metallic phase is composed of Pb-Bi alloy. The agglomeration tendency increases with increasing Pb content.

E.M.F. Cell Set-up and Thermodynamic Investigation of Liquid Pb-Bi Alloys at 550 and 575 °C

E.M.F. Cell Set-up and Thermodynamic Investigation of Liquid Pb-Bi Alloys at 550 and 575 °C

Effect of Magnetic Field on Periodic Structure Formation in Pb–Bi and Sn–Cd Peritectic Alloys

Unidirectional solidification of Pb-33 at%Bi and Sn-1.0 at%Cd alloys was performed under magnetic fields up to 8 MA/m (10 T). The rejection of the lighter Bi at the solidifying front strongly initiates the convection in the Pb-Bi alloy, while the rejection of the heavier Cd stabilizes the diffusion layer in the Sn-Cd alloy. For the Pb-33 at%Bi alloy, a periodic structure was observed at growth rates of 0.42 and 0.56μm/s under any magnetic fields up to 8 MA/m. The imposition of the magnetic field clearly increased length of the periodic structure formation. On the other hand, no significant effect of the magnetic fields on the banded structure was observed for the Sn-1.0 at% Cd alloy. The experimental results were consistently explained by the proposed model that considered instability of the side-by-side growth. The periodic structure originated in the peritectic systems itself and the unsteady flow in melt may act as a trigger. The periodic structure observed in peritectic systems can he generalized as the dissipative structure.

Flux creep and irreversibility line in superconducting Pb-Bi alloys

The critical current density, J/sub c/, in high-temperature superconductors becomes zero at irreversibility field, B/sub irr/, appreciably lower than the upper critical fields, B/sub c2/. The enhancement of J/sub c/ and B/sub irr/ is one of the crucial subjects to be attained. In high-temperature superconductors, conclusive result has not yet been presented because of the complexity of the material structure and in low-temperature superconductors scientific interest has not been paid because of the vanishingly small deviation of B/sub irr/ from B/sub c2/. In this study, we'll apply a simple system of low-temperature superconductor Pb-Bi, whose pinning characteristics were fully examined and controllable, to understand the relation of B/sub irr/ and the pinning mechanism. Observed irreversibility field, B/sub irr/, is discussed using the pinning characteristics and numerical calculation based on the flux creep theory. Magnetic relaxation caused by the flux creep was also observed by SQUID magnetometer. The relation of the apparent pinning potentials, U*/sub 0/, estimated from the flux creep rate and the irreversibility field, B/sub irr/, are studied.

Visualization of Simulated Molten-Fuel Behavior in a Pressure Vessel Lower Head Using High-Frame-Rate Neutron Radiography

High-frame-rate neutron radiography is used to observe the behavior of a high-temperature (≤773 K) molten Pb-Bi alloy dropped into a vessel that contains water. Experiments are also performed with an empty vessel. Using high-speed cameras combined with image intensifiers and a high-flux neutron source, the interactions among the molten and solidified alloy with water and steam are visualized at imaging rates of 500 and 125 frames/s. The behavior of the melt and steam bubbles is observed clearly in contrast to water. Observation of AuCd3 tracer particles in the molten metal dropped into the vessel that contains water is also successful. The velocity distribution in the melt is measured successfully by means of particle image velocimetry (PIV) using tracer particles. This visualization technique proves to be a promising tool to observe and measure the rapid and complex phenomena of a metal-gas-liquid mixture.

Low-temperature plasticity of Pb–Bi alloys: the role of thermal activation and inertial effects

Detailed studies of temperature dependences of critical shear stress and strain-rate sensitivity of deforming stress of Pb–Bi single crystals with 0.1–6.0 at. % Bi are carried out in the temperature range 0.5–295 K. The deforming stress decrease during a superconducting transition of the sample is studied and the concentration dependence of the effect is measured. The ideas of a gradual transition (upon cooling) from thermally activated motion of dislocations through impurity barriers to the thermoinertial mechanism in the temperature range 10–25 K and further to the quantum-inertial motion at temperatures ≲1 K are developed. A detailed thermoactivation analysis of experimental data is carried out, and empirical estimates of internal stresses, dislocation–impurity interaction parameters, electron and phonon components of dynamic drag coefficient for dislocations are obtained.

Co-segregation at the surface of Pb-Bi-Ni alloys: combined ab initio and Monte Carlo study

A recent study of a Pb-Bi-Ni alloy containing 5 at.% Bi and 0.04 at.% Ni reported a strong co-segregation of Bi and Ni at the alloy surface. We have performed ab initio calculations of the segregation profiles at the (111), (100) and (110) surfaces of random alloys by means of the coherent potential approximation and the tight-binding linear muffin-tin-orbitals method. We have found the segregation profiles to be oscillatory (this effect is most pronounced for the (111) surface) with a strong preference for Bi to segregate to the first atom layer and depletion of Bi in the subsurface atom layer. The energetic origin of the oscillatory segregation is discussed in terms of the Connolly-Williams effective cluster interactions. In the ternary alloy we have also found a tendency for Ni to segregate to the subsurface atom layer due its strong interaction with Bi, which is present at high concentrations relative to the bulk in both the first and third atom layers of the (111) surface. In order to include relaxation effects, we have performed Monte Carlo simulations, employing Finnis-Sinclair-type empirical many-body potentials, and computed the segregation profiles at the (111) surface of and alloys. For Pb-Bi alloys, the concentration profiles have also been found to be oscillatory, in fair agreement with results of the ab initio calculations. The calculations on Pb-Bi-Ni show strong segregation of Ni to the subsurface atom layer, accompanied by co-segregation of Bi to several of the outermost atom layers.

Phase separation and solidification of immiscible metallic alloys under low gravity

Alloy melts being immiscible in the liquid state separate on earth rapidly by Stokes sedimentation of the droplets of the minority phase being nucleated and grown during cooling through the miscibility gap. Their Marangoni motion is, however, of similar importance to the evolving microstructure during a casting process, since ahead of the solidification front temperature gradients exist. The joint action of Stokes and Marangoni-motion determines the microstructure of castings on earth. In space using the EuroMIR'95 mission and parabolic flights in fall of 94 and 95 we investigated the effect of Marangoni motion alone on the microstructure during casting and directional solidification of AlPb, AlBi and AlPbBi alloys. The experimental results on earth and under low gravity are described with a population dynamical model analytically and with a numerical model. The experiments and the quantitative description of the microstructure give new insights into the role of Marangoni motion and coagulation processes between droplets.