To understanding of slow and non-monotonic relaxation in Al–Y eutectic melts

•Explanation of the phenomenon of slow non-monotonic relaxation of eutectic melts is discussed.•We argue slow dynamics is result of non-linear diffusion in initially non-homogenous sample.•The system evolution described by the Cahn-Hilliard equation with uphill diffusion.•Fluctuations accounting in the considered model allows describe the non-monotonic relaxation. We discuss the nature of slow relaxation processes in glass-forming eutectic melts right after melting. For specific, we focus on the binary metallic melt Al–Y, which in addition to the slow relaxation shows unusual non-monotonic dynamics. We argue this slow dynamic the result of non-linearity of diffusion processes in the initially non-homogenous sample, and the nature of slow relaxation processes in eutectic melts after melting is similar to the nature of spinodal decomposition when the reason for the slowdown is the thermodynamic instability. To support this assertion we considered the model with combined Gibbs potential of the Al-Y liquid solution, in which the presence of the stoichiometric phase remains is taken into account. We show that in this system the instability mathematically described by the Cahn–Hilliard type equation can develop, and that fluctuation accounting in the considered model allows qualitatively describe the non-monotonic relaxation observed in the Al-based non-equilibrium melts.