The Diffusion Isotope Effect and Diffusion Mechanism in Liquid Cu-Ag and Cu-Ni Alloys

In this paper, the diffusion isotope effect and diffusion mechanism are investigated by means of molecular dynamics simulations in two liquid alloys, Ni-Ag and Ni-Cu. The values for the diffusion isotope effect parameter allow for the estimate of the number of atoms which are moving cooperatively in a basic diffusion event as experienced by a given atomic species. It is shown that the composition dependence of ND is typically very small. However, the temperature dependence of this parameter is much more pronounced. In addition, it is shown that, on average, in these alloys and temperatures considered, ND is limited to the range: 5<ND<17. This is consistent with results of molecular dynamics simulations on the average coordination number calculations. This would suggest that, together with a given atom, depending on temperature, the neighbouring atoms are all involved in the basic diffusion event.

DETERMINATION AND MODELING OF THE LIQUIDUS SURFACE, VAPOR PRESSURE AND IMMISCIBILITY BOUNDARIES IN THE Cu–Pb–S SYSTEM

For the first time using a membrane zero-manometer, the vapor pressure S2 over the surface of the PbS liquidus in the ternary system Cu–Pb–S were determined in the range 1100÷1400 K and 0÷760 mm Hg. Based on the thermodynamic calculation, the boundaries of the immiscibility of liquid alloys of the Cu–S, Pb–S, and Cu–Pb–S systems were determined and analytically described. Critical temperatures and pressures for immiscibility regions of sulfur-rich liquid alloys are characterized by high values: Tcr= 1520÷1880 K; Pcr=170÷510 atm. The crystallization surfaces of lead sulfide with electronic conductivity (p-type PbS) and with hole conductivity (n-type PbS) are calculated and analytically de-scribed, as well as the corresponding values of sulfur vapor pressure over the crystallization surface of lead sulfide. All analytical dependencies for 3D modeling were obtained and visualized using the OriginLab computer program

The interdiffusion in liquid alloys of alkali metals with lead

The mutual diffusion in liquid cesium-lead alloys containing from 20 to 70 at.% Pb is investigated by a gamma-ray attenuation technique. The obtained data are compared with the results of similar studies for Li-Pb, Na-Pb, and K-Pb melts, carried out by us earlier. The concentration dependences of the interdiffusion coefficient for alkali-lead liquid systems demonstrate pronounced maxima in the vicinity of 20 or 50 at.% Pb. These phenomena confirm a tendency for chemical short-range ordering in liquid alloys.

Dissimilar Metal Solution from Solid Alloys as Observed for Steels and Nickel‐Based Alloys in the Presence of Lead‐Based Liquid Alloys or Liquid Tin

The solution of elements from metallic alloys is analyzed, notably the initial stage characterized by solution in proportion to the alloy composition and subsequent selective leaching of alloying elements. For the latter stage of the process, characteristic features of the originating depletion zone are derived for different formation mechanisms. The results are compared with observations for steels and nickel-based alloys after exposure to lead-based liquid alloys or liquid tin, and, where possible, the prevailing mechanism is identified. Furthermore, the influence of dissolved oxygen and formation of intermetallic compounds are addressed.

Theoretical assessment for the mixing properties of AlMg liquid alloys at 1073K

The alloying behavior of AlMg alloy in the liquid form at 1073 K has been theoretically investigated in the framework of four-parameter model which is based on Maclaurin series. The analytical expressions for thermodynamic functions such as excess free mixing energy, free mixing energy, enthalpy of mixing and entropy of mixing and microscopic functions such as concentration fluctuations at the long wavelength limit and Warren-Cowley chemical short range order parameter have been derived. These expressions have been used to compute the excess Gibbs free energy of mixing, Gibbs free energy of mixing, activity, enthalpy(heat) of mixing, excess entropy of mixing, entropy of mixing, concentration fluctuations in long wavelength limit and Warren-Cowley short range order parameters of AlMg liquid alloys at 1073 K. The investigation shows the excellent concurrence between the experimental and theoretical measurements of the mixing properties of AlMg liquid alloys at 1073 K. Interaction parameters of energy depends on temperature.

Enthalpies of mixing in ternary Al–Gd–Mn liquid alloys

The enthalpies of mixing in liquid alloys of the ternary Al–Gd–Mn system were determined over a wide range of compositions by means of isoperibolic calorimetry at 1650 K. The measurements of the partial enthalpies of components were performed along five sections: for the ΔH̅ Al (sections with x Gd/x Mn = 0.30/0.70 and 0.65/0.35 for x Al changed from 0 up to 0.30); for the ΔH̅ Gd (x Al/x Mn = 0.80/ 0.20 and 0.50/0.50 for x Gd changed from 0 up to 0.30); for the ΔH̅ Mn (x Al/x Gd = 0.29/0.71 for x Mn changed from 0 up to 0.26). The enthalpies of mixing in the ternary system were found to be exothermic and steadily increasing in absolute values from the Mn corner towards the Al–Gd constituent binary system, reaching the minimum value of approximately – 37 kJ · mol–1 in the vicinity of the Al0.6Gd0.4 composition, evidently related to the formation of stable Al2Gd phase.