Pattern formation during melting of lamellar eutectics

TL;DR

This study combines experiments and simulations to analyze pattern formation during the melting of lamellar eutectics, revealing diverse patterns and underlying physical mechanisms.

Contribution

It introduces a combined experimental and phase field simulation approach to understand melting patterns and scaling behaviors in lamellar eutectic systems.

Findings

Good agreement between experiments and simulations on pattern diversity.

Identified scaling laws for liquid penetration and finger thickening.

Discovered a period-doubling instability at small lamellar spacings.

Abstract

We present a study of the melting dynamics of a two-phase eutectic solid. In situ, thin-sample experiments using a transparent eutectic alloy and two-dimensional phase field simulations calibrated for the very same alloy are combined to assess pattern formation during directional melting in a temperature gradient. Depending on the melting velocity $V_m$ and the spacing $\lambda$ of the pre-solidified lamellar microstructure, an unexpectedly rich diversity of melting patterns is observed, with good agreement between experiments and simulations. We unravel the different physical mechanisms leading to this diversity, and establish the scaling behaviors of (i) the penetration of the liquid along the solid-solid interface at large $V_m$, (ii) the thickening of the primary-phase fingers at low $V_m$, and (iii) a period-doubling instability for small $\lambda$ values. Our study provides a fundamental basis for further investigations of eutectic melting, including additive manufacturing during which melting/solidification cycles take place.