Crystal plasticity model for predicting ductile fracture in cast Al alloy

Abstract

Ductile fracture in die-cast Al–Si–Mg alloys is critically influenced by the cracking of brittle eutectic Si particles embedded in a ductile Al matrix. Accurately capturing this microstructurally driven fracture behavior is essential for understanding and predicting fracture in the corresponding cast material. This study presents a crystal plasticity finite element model that explicitly incorporates three key damage mechanisms: void nucleation and growth, shear-driven damage, and—for the first time—cracking of eutectic Si particles based on a stress-based criterion informed by Eshelby's inclusion theory. The model captures the evolution of damage under varying triaxiality and Lode angle conditions, enabling realistic simulation of fracture behavior across diverse stress states. On the experimental side, key microstructural parameters such as void volume fraction and Si particle size and morphology were quantified, and mechanical tests were conducted on specimens with different geometries to provide broad validation data. The model accurately reproduced the measured flow stress and fracture strain trends, demonstrating strong agreement with experimental observations. By establishing a direct link between microstructure and macroscopic fracture behavior, this work provides new mechanistic insights into the role of Si particle cracking in ductile fracture and extends the applicability of crystal plasticity models to cast Al alloys.