# Diffusion Behavior and Fracture Mechanism at Solid–Liquid Interface of Polycrystalline Al/Mg Bimetallic System: A Molecular Dynamics Simulation

## TL;DR

This study uses molecular dynamics simulations to explore how temperature affects the diffusion and fracture behavior of Al/Mg bimetallic composites, offering insights for optimizing their performance.

## Contribution

The paper reveals distinct effects of pouring and preheating temperatures on diffusion and fracture mechanisms in Al/Mg bimetallic systems.

## Key findings

- Mg atoms diffuse faster than Al atoms, but Al atoms travel farther at the interface.
- Higher temperatures increase the thickness of the interfacial transition layer.
- Optimal tensile strength of 1.850 GPa is achieved at 923 K pouring and 473 K preheating temperatures.

## Abstract

Al/Mg bimetallic composites have drawn considerable attention for their promising lightweight applications in sectors such as the aerospace and automotive industries. In these systems, the interfacial behavior critically governs the overall performance and reliability. In this research, the molecular dynamics (MD) simulation was employed to systematically study the effects of pouring temperatures (923 K, 973 K, and 1023 K) and preheating temperatures (373 K, 473 K, and 573 K) on the interfacial diffusion behavior and fracture mechanism of the polycrystalline Al/Mg bimetallic system. The results indicate that the influencing rule of pouring temperatures and preheating temperatures on the interfacial diffusion behavior is consistent. Specifically, the diffusion coefficient of Mg atoms is higher than that of Al atoms, while the diffusion distance of Al atoms is significantly greater than that of Mg atoms. As the temperature increases, the thickness of the interfacial transition layer correspondingly rises. However, the effects of these two parameters on tensile fracture behavior demonstrate notable discrepancies. Specifically, the fracture mode evolves with pouring temperature, transitioning from being mediated solely by dislocations to being co-mediated by twins and dislocations. In contrast, the fracture mechanism remains solely dislocation-controlled, regardless of the preheating temperature. In addition, all the models fractured at the interface between the diffusion layer and the Mg matrix. The optimal tensile strength of 1.850 GPa was achieved at a pouring temperature of 923 K and a preheating temperature of 473 K, representing an improvement of approximately 52% compared to the lowest value recorded in the study. This research offers significant theoretical insights for the rational optimization of preparation parameters and an in-depth understanding of fracture mechanisms in Al/Mg bimetallic systems.