On Spontaneous Dispersion as a Cause of Microstratification of Metal Melts

The phenomenon of spontaneous dispersion is considered as the cause of the microstratification of metal melts. In a microstratification melt, a violation of long-range order in the arrangement of atoms (LRO) is observed, which corresponds to a dispersed particle size of more than 2 nm. Microseparation occurs due to spontaneous dispersion upon contact of liquid and solid metal or the mixing of two liquid metals. The possibility of spontaneous dispersion was assessed using three different criteria: Volmer's cr iterion, Rehbinder's criterion and the diffusion rate criterion. The diffusion rate criterion was obtained on the basis of the theory of rate processes, which describes how diffusing atoms overcome the interphase boundary. It has been established that Al-Sn melts contain colloidal-scale particles (4 nm), and Al-Si and Al-Ge melts contain atomic-scale particles (0.1 nm). For a system with a continuous series of Cu-Ni solid solutions in dispersion (Cu10Ni90-Cu20Ni80), the particle size is 2 nm. The particle size of the ternary eutectic GaInSn in the dispersion (Ga50In50-Ga50Sn50) is 5.6 nm, and the size of immiscible Cu-Fe melts in the dispersion (Cu80Fe20-Cu60Fe40) is 4.8 nm. Long-range order violations (LRO) and the presence of microlayering with colloidal particles larger than 20 nm were observed in the GaInSn ternary eutectic, in the Al-Sn simple eutectic with the preferential interaction of similar atoms, and in Cu-Fe melts with a monotectic phase diagram.

Kinematic Viscosity ofMulticomponent FeCuNbSiB-BasedMelts

The work investigated the temperature dependences of the kinematic viscosity for multicomponent melts of nanocrystalline soft magnetic alloys. It is shown that there is a linear relationship between the reduced activation energy of viscous flow E_a·(RT)⁻¹ and the pre-exponential factor ν₀. This ratio is universal for all quantities, the temperature dependence of which is expressed by the Arrhenius equation. It is shown that the activation energy of a viscous flow is linearly related to the cluster size on a natural logarithmic scale, and the melt viscosity increases with decreasing cluster size. The change in the Arrhenius plot in the anomalous zone on the temperature dependence of viscosity can be interpreted as a liquid–liquid structure transition, which begins with the disintegration of clusters and ends with the formation of a new cluster structure.