Toughening mechanisms of a Ti-based nanostructured composite containing ductile dendrites

The compressive deformation behavior of a multi-component Ti–Cu –Ni –Sn –Nb composite containing ductile dendritic precipitates embedded in a nanostructured matrix was investigated. The Ti-based composite not only displays a high compressive plasticity of ≈ 21 %, but also exhibits a high fracture strength of ≈1.8 GPa, which is comparable to that of monolithic bulk metallic glasses. Pronounced work hardening was observed after yielding. The surface deformation morphology reveals that the work-hardening behavior of the composite is related to the plastic deformation of the dendritic phase and the interaction of shear bands in the nanostructured matrix with the hardened dendrites. At the final stage of compression, most of the dendrites are work hardened, whereby the propagation of the shear bands in the matrix is retarded. The strong interaction between the dendrites and the matrix contributes to the high strength and plastic deformation capability of the composite. The fracture surface exhibits viscous flow traces, indicating that softening or melting of the composite occurs at the moment of fracture, due to the release of the high elastic energy stored in the specimen.