Structural changes in the melt of a heat-resistant nickel alloy as phase transition of the second order

Abstract

Information about the behavior of melts of the high-temperature nickel alloys is the basis for creating new smelting technologies that significantly increase the service properties of metal products, as well as solve a number of technological problems. The results of numerous studies indicate structural changes occurring in various metal melts under the influence of temperature and time. For many years, there has been a scientific discussion about the nature of these phenomena, and a common opinion was formulated on a number of issues. Structural changes in metallic liquids are presented as a second-order phase transition, where a liquid of higher density is replaced by a liquid of lower density. These transformations in the structures of liquid metals are called liquid-liquid transition (LLT). Studies of the structure-sensitive properties of melts of the heat-resistant nickel alloys also reveal structural changes that irreversibly transform the melt into a microhomogeneous state. The research results presented in this article confirmed that structural changes in melts of the high-temperature nickel alloys are also a second-order phase transition, as evidenced by the breakage of atomic microgroups, uniform redistribution of alloying elements, and the formation of new clusters characterized by smaller sizes and greater chemical homogeneity. Therefore, these changes can be characterized as LLT, while this does not contradict the previously substantiated quasi-crystalline model of the microinhomogeneous state of liquid heat-resistant nickel alloys.