Microsegregation in Ion-Electron Liquids: Molten Metals and Alloys

Abstract

A number of experimental studies of different physical and chemical properties and microstructure analysis revealed structure transformations in liquid metal alloys during solidification, especially near melting temperature (T m ). A complicated microstructure behavior was found in metal systems with different type of interatomic interactions (eutectics, monotectics and systems with intermetallic compounds in the solid state). Furthermore, pure liquid metals and semimetals have also indicated microstructure changes in the temperature region near the melting points. Several models describing such microstructure transformation are based on microsegregation processes resulting in the formation of microregions with different arrangement in the liquid matrix. F. Sommer proposed the association model to describe temperature and concentration dependencies of thermodynamic properties (enthalpies of mixing chemical activity etc.). According to this model chemical short-range ordered atom regions exist in the alloys with strong chemical interaction between atoms. Another approach is the quasieutectic model proposed by E. Kalashnikov which suggests the quasieutectic or statistical and intermediate atom distribution in the liquid state near Tm. Based on structure-sensitive properties a complex analysis of the microstructural changes during solidification in some eutectic and near eutectic alloys was carried out. The above mentioned models were used to perform quantitative estimation of the formed microregions with atomic concentration different from the statistical distribution. Based on the obtained results the overall picture of microsegregation processes in the liquid metals and metal alloys regardless of the preferred type of interatomic interactions has been obtained.