Metastable Colloidal States of Liquid Metallic Solutions

Branching of curves produced during the heating and subsequent cooling process after sample melting was observed while investigating the temperature dependences of liquid alloy properties. The given phenomenon was observed only when the initial materials had a heterogeneous crystalline structure. This is associated with conservation of microscopic inhomogeneities (1-10 nm) in the melt, inherited from the initial materials or appearing when the components are mixed near the liquidus. Such aggregates represent a disperse phase enriched with one of the components being in metastable equilibrium with the dispersion phase of a different composition. The colloidal state is irreversibly destroyed with temperature increase to values T hom characteristic of the given composition. Then the system transfers to the state of a true solution which is stable in the entire zone above liquidus. The introduction of surface-active elements that reduce the interface tension at the boundaries of colloidal particles leads to destruction of microheterogeneity at lower temperatures. After transition of the system to a true solution state, the ingot or metallic glass structure which forms on cooling or quenching changes greatly. In systems with immiscibility gaps, one can get a macrohomogeneous fine-disperse structure of the frozen emulsion. In the Cahn-Hilliard approximation, the authors analyse the model system including a disperse particle weighted in a dispersion phase of another composition, confirming the concept.