Research of melt stratification in Cu-Pb system using the pulse-phase method

Stratification in liquids plays an important role in dividing substances through extraction, this is why it should be studied very closely. What is more, melt stratification is interesting from the point of view of critical phenomena physics in condensed systems. However, up until now stratification in nontransparent liquids, in particular in metal and semi-conductor melts have not been sufficiently studied. Out of 80 double systems that show stratification when in liquid state, only a few have experimental data reflecting the dome of the two-phase field L1 + L2. All of the other only have their field borders marked with dotted lines. The analysis of the reference material from a later period of time has indicated that the situation with the research of stratification fields has hardly changed. In our opinion, such a situation results from the lack of an experimental method that would allow to accurately establish the position of a monovariant equilibrium line limiting the stratification field in liquid state. Today in order to solve this problem, the following methods are employed most often: electrical conductivity measurement, viscosity, density, differential and thermal analysis, quenching in liquid state with further metallographic analysis, etc. We researched the stratification field in the Cu-Pb system with the pulse and phase method. A line of monovariant equilibrium limiting the specified field is constructed on the basis of experimental data. The coordinates of the critical point are established: temperature - (1271 ± 2) K, contents - 0.35 atomic fraction Pb, the rest is Cu. This paper shows that the pulse and phase method can be successfully used to accurately establish the liquid stratification border in a phase diagram, Tcr of stratification and also to study the stratification process itself.