Detection of the LLT in Superalloys Melts Upon Overheating and Relaxation by the Electromagnetic Method

Abstract

Among numerous melt structure model representations, the most relevant for liquid heat-resistant nickel alloys description is the quasicrystalline model of microinhomogeneous structure, in which it is assumed that multicomponent nickel melts consist of clusters and intercluster space. Clusters inherit the short-range order of the atomic structure from various phases of the initial solid metal crystalline structure. Heating the melt to a certain temperature and/or increasing a period of its isothermal holding at constant pressure leads to a second-order phase LLT transition. As a result, atomic associations which are more balanced and uniformly distributed over the melt volume are formed. Structural changes in nickel superalloy melts are irreversible and have a significant effect on the formation of the structure and properties of a solid metal during crystallization. Structural LLT changes in multicomponent nickel melts are the basis for the scientific substantiation of technological modes of smelting, which contribute to improving the technological properties of melts, reducing metallurgical defects, the rational use of expensive elements and foundry waste, as well as, a significant improvement in the quality of metal products. This work is devoted to the experimental determination of the LLT transition in superalloy melts by the noninvasive electromagnetic method.