# Multiscale Simulation of Crack Propagation in Impact-Welded Al4Cu9 Alloy Based on Cohesive Zone Model

## TL;DR

This study combines simulations and experiments to understand how cracks spread in impact-welded Cu/Al joints, focusing on the Al4Cu9 interface.

## Contribution

The paper introduces an integrated multiscale approach combining MD, FE, and CZM with experimental validation to study crack propagation in Cu/Al joints.

## Key findings

- Composite defects reduce fracture energy and stress intensity more than single defects.
- Defect effects are more significant than temperature effects in the studied range.
- Simulation predictions align with experimentally observed crack initiation locations.

## Abstract

The fracture behavior of the Al4Cu9 intermetallic compound at the interface of impact-welded Cu/Al joints remains insufficiently explored through integrated multiscale modeling and experimental validation. In this study, molecular dynamic (MD) simulations, finite element (FE) analysis implemented in ABAQUS (version 2020) and a cohesive zone model (CZM) were combined with optical microscopy (OM) and scanning electron microscopy (SEM) observations of the interface and crack initiation zones in impact-welded Cu/Al specimens to investigate crack propagation mechanisms under different defect configurations. The experimental specimens consisted of 1060 aluminum (Al) and oxygen-free high-conductivity (OFHC) copper, fabricated via impact welding and subsequently annealed at 250 °C for 100 h. The interfacial morphology and crack initiation features obtained from OM and SEM provided direct validation for the traction–separation (T-S) parameters extracted from MD and mapped into the FE model. The results indicate that composite defects (blunt crack + void) cause a significantly greater reduction in fracture energy and stress intensity factor than single defects and that defect effects outweigh temperature effects within the range of 200–500 K. The experimentally observed crack initiation locations were in strong agreement with simulation predictions. This integrated simulation–experiment approach not only elucidates the multiscale fracture mechanisms of the Al4Cu9 interface but also provides a physically validated basis for the reliability assessment and optimization of aerospace Cu/Al welded structures.