Damage-Coupled Crystal Plasticity Model for Predicting Ductile Fracture Behavior of Cast Al–Si–Mg Alloy

Abstract

The ductile fracture behavior of an Al–Si–Mg alloy—governed predominantly by the cracking of eutectic Si particles embedded in the Al matrix—was investigated through both experimental and theoretical approaches. On the theoretical side, a novel constitutive model within the crystal plasticity framework was developed to simulate ductile fracture by incorporating both void evolution and eutectic Si particle cracking. To the best of our knowledge, this study presents the first attempt to explicitly integrate the cracking behavior of eutectic Si particles into a crystal plasticity finite element model, enabling a more mechanistic understanding of microstructurally driven fracture. Void evolution was modeled through nucleation, growth, and coalescence mechanisms, as in classical Gurson-type damage models, while the fracture of Si particles was described using a stress-based criterion informed by Eshelby’s inclusion theory to capture local particle stress. Additionally, damage from shear deformation was accounted for to better reflect complex stress states. On the experimental side, key microstructural features such as void volume fraction, and Si particle size and volume fraction were quantified. Mechanical tests with diverse sample geometries were conducted to span a wide range of stress triaxiality and Lode angle conditions. The predictions from the proposed crystal plasticity model showed strong agreement with experimental results, both in terms of flow response and fracture strain. Overall, this study provides new insights into the fracture mechanisms of Al–Si–Mg alloys by establishing a direct link between microstructural features and macroscopic fracture behavior—with particular emphasis on the pioneering incorporation of Si particle cracking into the CPFE framework.

Keywords: Crystal plasticity, Eshelby inclusion theory, Eutectic Si, Damage modeling