About causes of slow relaxation of melted intermetallic alloys

TL;DR

This paper investigates the slow relaxation phenomena in melted intermetallic alloys, attributing it to nonlinear diffusion processes caused by thermodynamic instability in heterogeneous melts with inclusions.

Contribution

It introduces a model based on the Cahn-Hilliard equation to explain slow relaxation in alloys, highlighting the role of initial heterogeneity and phase instability.

Findings

Heterogeneity leads to thermodynamic instability causing slow relaxation.

Model predicts regions of instability in phase diagrams.

Application to Al-Y and Al-Yb alloys confirms the theory.

Abstract

Ascertainment of the nature of the slow relaxation processes observed after melting in glass-forming eutectic melts is the subject of this work. We claim that the diffusion processes nonlinearity in heterogeneous melt with inclusions of refractory stoichiometry is the origin of this phenomenon. The cause for this nonlinearity is the thermodynamic instability similar to one taking place at spinodal decomposition, and indispensable condition is the initially non-homogenous. For confirmation of our devotes, we consider the model of liquid solution of a binary system, which evolution described by the Cahn-Hilliard equation with combined Gibbs potential assuming the presence of remains after melting stoichiometric phase. Exemplified by the Al-Y and Al-Yb alloys, using Gibbs potentials from a standard database we show that subject to initial heterogeneity in these systems the instability can develop leading to the slow relaxation processes, and determine the regions of this instability in the phase diagrams.