Stress-Assisted Structural Phase Transformation Enhances Ductility in Mo/Cu Bicontinuous Intertwined Composites

We use molecular dynamics simulations to demonstrate a homogeneous two-step structural phase transformation in the molybdenum (Mo) phase of a Mo/Cu bicontinuous intertwined composite during tensile loading. The Mo atoms first transform from a ⟨001⟩-oriented body-centered cubic structure to a ⟨001⟩-oriented face-centered cubic structure via the Bain transformation. Then they further transform to a ⟨110⟩-oriented body-centered cubic via the Pitsch transformation. This homogeneous transformation results in a novel stress–strain behavior with extended plastic deformation of the whole material. Stress state analysis indicates that the driving force for this structural phase transformation is the large tensile stress induced by interfaces in the bicontinuous intertwined structure. Our results suggest new strategies for improving the ductility of ultrastrong nanocomposite metals.