Melting of alloys along grain boundaries

TL;DR

This paper models the melting of alloys along grain boundaries as a free boundary problem involving two moving interfaces, highlighting the role of triple junctions and diffusion in the liquid layer in controlling melting dynamics.

Contribution

It introduces a new free boundary model for alloy melting along grain boundaries considering the interaction of two interfaces and the influence of triple junctions.

Findings

The liquid film migration mechanism is more efficient due to diffusion control.

Weak coherency strain energy drives the LFM in one-phase alloys.

Melting with a single front is slower due to solid-phase diffusion.

Abstract

We discuss melting of alloys along grain boundaries as a free boundary problem for two moving solid-liquid interfaces. One of them is the melting front and the other is the solidification front. The presence of the triple junction plays an important role in controlling the velocity of this process. The interfaces strongly interact via the diffusion field in the thin liquid layer between them. In the liquid film migration (LFM) mechanism the system chooses a more efficient kinetic path, which is controlled by diffusion in the liquid film on relatively short distances. However, only weak coherency strain energy is the effective driving force for LFM in the case of melting of one-phase alloys. The process with only one melting front would be controlled by the very slow diffusion in the mother solid phase on relatively large distances.