Examining the mechanics responsible for strain delocalization in metallic glass matrix composites

Metallic glass matrix composites (MGMCs) represent a promising avenue for enhancing the ductility of monolithic metallic glass. These composites utilize a secondary crystalline phase to aid in the delocalization of strain. This work seeks to understand the mechanisms underlying strain delocalization in MGMCs to guide further advancements in this class of material. Employing a mesoscale shear transformation zone (STZ) dynamics model, we investigate how variation in dendritic microstructural sizes and spacings impact the shear banding behaviors of MGMCs subjected to uniaxial tensile loading. Statistical analysis of shear banding characteristics reveals that the competition of shear band nucleation and propagation rates can encourage strain delocalization in MGMCs. The introduction of a crystalline dendritic structure into the amorphous matrix increases the number of shear band nucleation events while reducing shear band propagation rates. Furthermore, reducing dendrite sizes leads to greater strain delocalization among more shear bands and delays the onset of run-away shear bands, resulting in lower overall shear band growth rates. Therefore, this study sheds light on the crucial role of dendritic microstructural sizes in influencing shear banding characteristics and strain delocalization in MGMCs, offering valuable insights to inform the design and development of advanced materials with superior mechanical properties.