Graphene interfaces regulate fracture in metallic glass based composites

The structural application of metallic glasses (MGs) is hindered by their propensity for catastrophic brittle fracture, which originates from the uncontrolled activity of shear transformation zones (STZs). Establishing a mechanistic linkage between atomic-scale STZ dynamics and macroscopic failure modes remains a defining challenge in advancing the plasticity of MG composites. Here, we employ architected graphene nanosheets as a unique stress-state modulator to tailor the cracking behavior of MG composites. We demonstrate a systematic transition in failure mode from brittle cavitation in monolithic MGs to shear banding, and ultimately to confined plastic necking in composites with optimally distributed graphene. This transition is attributed to the graphene-induced reduction in stress triaxiality, which biases STZ activity from dilatation- to shear-dominated modes. This work provides atomic-scale insights for engineering tough amorphous composites by leveraging internal interfaces to modulate stress states and decouple the shear-dilatation competition within STZs, a principle transferable to other disordered solids.