Melts microheterogeneity in binary metallic systems having eutectic and monotectic transformations

Abstract

The distinctive features of limited solubility in liquid eutectic and monotectic metallic systems have been discovered. The monodispersed emulsion model has been elaborated for a description of the specific microheterogeneous structure of eutectic melts. It includes the transitional shells (TS) at the interface boundaries having the eutectic composition and the closest packing of atoms. By means of the thermodynamic analysis a possibility of a metastable equilibrium of the emulsion has been determined when dimensional and interface energy parameters of the emulsion adopt certain values. The metastable state is characterized by the colloidal sizes of disperse particles and the interface tension values typical for immiscible melts. The existence of the emulsion has been confirmed by the calorimetric experimental data on Sn-Pb and Al-Si systems. Structure factors and RDF`s of the TS have been calculated by the original treatment of experimental diffraction data on Sn-Pb and Ag-Ge melts. The evidence of different microheterogeneity scales in liquid eutectic and monotectic systems has been obtained. From two immiscible phases only the liquid based on the light-melted metal shows the short-range microinhomogeneity and the second one is a homogeneous solution. So, the microheterogeneity in eutectic and monotectic melts has different nature.

Mechanical Spectroscopy Investigation of Liquid Pb-Bi Alloys

“…Maximum O present in all the investigated alloys can be tentatively explained by assuming that atomic bonds typical of the solid structure still exist in the melts not far from liquidus. As demonstrated for several metallic melts with eutectic phase diagram[17][18], it is likely that also the structure of Pb-Bi melts is heterogeneous when temperature is a little above liquidus. As temperature increases atoms gain higher and higher energy till that becomes high enough to break the residual Pb-Pb and Bi-Bi atomic bonds and form Pb-Bi mixed bonds, typical of an homogeneous liquid.…”

Metastable microheterogeneity in liquid monotectic Bi–Ga alloys

“…Zhukova et al 17 has elaborated an emulsion model for the description of microheterogeneity in binary eutectic metallic melts. For a binary A-B system, after melting, it does not turn to the thermodynamically stable solution but consists of three liquid phases: the dispersed small particles or microdroplets enriched in the higher melting point element B, the dispersed medium enriched in the lower melting point component A and the transitional shells at the interface boundaries.…”