Strengthening mechanism and plasticity deformation of crystalline/amorphous Cu3Fe/Fe3Cu nanolayered composite

Metallic glasses possess high strength and excellent elastic properties due to their amorphous atomic structure. However, they often display brittleness and suffer catastrophic failure because of shear localization, without exhibiting significant macroscopic plastic deformation under tension. In this paper, an effective method to enhance the strength and ductility of metallic glasses is presented by molecular dynamics simulation. The approach involves controlling the thickness of the crystalline Cu3Fe and amorphous Fe3Cu layers. The results indicate that increasing the thickness of the crystal layer improves the strength of the nanolayered composite. The crystalline/amorphous interface impedes stress propagation in the shear transformation zone, thereby enhancing the yield stress of the composite. Additionally, the presence of Hirth dislocations in the crystal layer strengthens the composite. The generation and annihilation of fixed dislocations in the crystal layer cause stress fluctuations in the composite, which further enhances its ductility. However, a small content of crystalline layer can cause stress concentration towards the shear band, leading to rapid fracture failure and reduced ductility. These findings shed light on the plastic deformation behavior of crystalline/amorphous composites at the nanoscale, providing valuable theoretical guidance for designing high-strength and ductile metallic materials.