The work is devoted to studying the transformation of the cluster structure of monoatomic metal melts Pb, In, Ga, Sn, and Bi at the formation of multicomponent liquid systems.
Unfortunately up to now there are no complete the general theory of liquid metals.This is especially important for profile analysis of diffraction peaks in SF and PCF, calculated from them. Due to widely use of the models of micro inhomogeneous structure of metal melts, it is necessary to show how the parameters of such inhomogeneities are related with profile features of SF and PCF.
Liquid metals can be considered from the viewpoint of quasi-polycrystalline model. This approach makes possible to explain the asymmetry of the first maximum and the presence of shoulder on its right hand side. But this theory isn’t used for finding a quantitative description of such microheterogeneous structure and of the relation between the physical properties of melts and their structure. In this work we attempt to obtain the some results on this problem.
Interpretation of the short-range order structure in the investigated melts was carried out within the framework of quasi-polycrystalline theory. As it was told the first maximum in the structural factor for liquid In, Ga, Sn, and Bi melts is characterized by the presence of asymmetry or hump. We assumed that asymmetry of principal peak is caused by the presence a more complicated structure in comparison with simple liquid metals, whose principal peaks show the symmetric shape. Therefore we compared the structure of these elements with the structure of the melt with symmetric maximum. Interpretation of the complicated structure of the main maximum profile in the structural factor for liquids systems was occurred in the additive superposition, ie under the assumption that the intensity of melt scattering is the sum of scatterings from individual microregions.
The asymmetry of the principal maximum in the structural factor for liquid indium is associated with the display of microheterogeneous structure and may be a quantitative measure of the structure deviation for the melt from the dense atomic package. We suppose that in liquid indium at least there are two kinds of such microregions – clusters, but with a different type of short-range order. The presence of two kinds of clusters with different packing densities in liquid indium is consistent with the fact that it has a tetragonal lattice in the solid state, which is not typical for classical metals. Instead, liquid melts of Ga, Sn, and Bi also reveal a shoulder on its right hand-side, which means a greater tendency to microheterogeneity in opposite to the indium melt. This micro-heterogeneity is also revealed in the existence of two kind clusters, but with different chemical bonding. A quantitative description of the main structural parameters for such clusters is proposed. In all cases each structural component of the melt is sensitive to temperature and reveals a different nature of the temperature dependence.
Position of this peak of binary Ga-Sn system lies between such peaks for liquid Ga and Sn, has significant width and as result can be interpreted as additive sum of curves, corresponding to SF for constituent elements. Therefore the SF supposes that eutectic melt and melt of nearequiatomic concentration consist the structural units, with like kind atoms.
The study of the InBiGaSn system using x-rays and electron microscopy also has shown the absence of random distribution of atoms in it. SF for equiatomic InGaSnBi alloy show principal peak. First of all there is a shoulder on right hand side of main maximum, which is observed also in SF for liquid Ga, Bi and Sn. But it is less pronounced comparing to similar shoulder in these three liquid metals. Obtained results from XRD and electron microscopy allowed us to point out that tendency to heterocoordinated atomic distributionis observed in quaternary InBiGaSn molten alloy. Structure of equiatomic quaternary InBiGaSn molten alloy is another than structure of each any constituent elements as well as for system of same atoms with random atomic distribution. Also we can conclude that the tendency to microhomogeneity is stronger in InBiGaSn melt to compare with the monoatomic investigated melts and the binary Ga-Sn melt of nearequiatomic concentration. In the case of the multicomponent equiatomic liquid system InPbGaSnСu, its structure is different than one of each any constituent element. The main structure parameters reveal a typical temperature behavior as in metal melts. Obtained results allowed us to suppose that there are two dominant tendencies at formation of multicomponent In20Pb20Ga20Sn20Cu20 melt.
For a more complete analysis, surface phenomena in these systems were studied using the sessile drop method. Obtained results on surface tension confirm our data on X-ray diffraction studies.
