A damage-tolerant Ti-rich multiphase metallic-glass composite with hierarchically heterogeneous architecture

Lightweight materials with good combinations of properties, such as high strength, ductility and damage tolerance, are highly desirable in engineering applications; nevertheless, it remains a challenge to “defeat” the generally exclusive relationships between different properties for structural materials. One viable means is to construct complicated architectures in materials. Here, we employ a lightweight Ti-based metallic glass (MG) and pure Ti as constituents and assemble them into a hierarchically-structured multiphase composite with tailored heterogeneity. The Ti-rich multiphase composite exhibits a relatively low density of 4.95 g∙cm−3 owing to its high Ti content and a high strength of ∼1408 MPa derived primarily from the MG phase. The hierarchical architecture with tailored heterogeneity promotes the formation of abundant shear bands and microcracks in MG, yet inhibits their extension to avoid catastrophic fracture, thereby endowing the Ti-rich multiphase composite with a remarkable tensile ductility of ∼7.1% which is nearly two times that of the MG composite having similar phase constitution but a uniform structure. Moreover, this architecture causes crack-tip blunting by promoting plastic deformation, together with crack bifurcation and microcracking ahead of the crack tip, which bestows a high (notched) fracture toughness of ∼109 MPa∙m1/2 which is around three times that of its counterpart. This study is intended to give insight for the architectural design of new materials by offering a viable means for their architectural construction to achieve good combinations of properties.