Mechanical Behavior Of In-situ Ti-based Metallic Glass Matrix Composites Upon High-strain-rate Dynamic Compression

Bulk metallic glasses(BMGs) possess many excellent mechanical properties, such as high strength, large elastic limit, and good wear resistance, which render them the potential as structural materials. However, almost all the BMGs exhibit catastrophic failure with brittleness upon loading at room temperature, due to the prompt propagation of highly localized shear bands. The mortal defect has extremely restricted wide applications for BMGs in the engineering field. In order to alleviate this problem, a series of in-situ dendrite reinforced metallic glass matrix composites(MGMCs) have been developed recently. The ductile dendrites are homogeneously distributed in the glass matrix, and can prevent the prompt propagation of shear bands, thus improving the plasticity.The mechanical properties of the in-situ MGMCs upon quasi-static loadings have been extensively investigated. In terms of the actual engineering applications for in-situ MGMCs, many extreme conditions such as high speed dynamic loading must be carefully considered. The information on the mechanical properties of the materials upon dynamic loading is of great importance, which can be effectively applied to strategic fields, such as defense, aerospace, and precision machinery. However, few studies on their dynamic behavior have been reported. Therefore, it is necessary to conduct more investigations on in-situ MGMCs and to classify the dynamic deformation behavior sufficiently.In this study, the dynamic deformation behavior of Ti-Zr-V-Cu-Be composites are investigated.Quasi-static and dynamic deformation behavior of Ti58Zr16V10Cu4Be12 composite are investigated. Upon quasi-static compression, the composite exhibits distinguished work-hardening capacity and the fracture strain approaches about 14.5%. The pile-ups of dislocation in the ductile dendrites accounts for the macroscopic plasticity of the composite. On the other hand, although the composites exhibit plasticity of only 2% upon dynamic compression, it has been a breakthrough compared with previous studies. Upon dynamic loading, the fracture strain decreases, due to the fact that there is not enough time for the initiation of multiple shear bands, leading to the decrease of the resistance to fracture.The influence of dendrite size on dynamic deformation behaviors are studied. The Ti40Zr24V12Cu5Be19 composite exhibits brittle fracture because the fine dendrites cannot retard the propagation of shear bands. In contrast, plasticity is available for the Ti48Zr18V12Cu5Be17 composite, due to plastic deformation of the coarse dendrites and effective obstruction to the propagation of shear bands.The Ti62Zr12V13Cu4Be9 composites exhibit distinguished plasticity upon dynamic loading. TEM and HRTEM are employed to reveal the deformation structure of the present composites upon dynamic loading. The ductile dendrites accommodate plasticity, characterized by the multiplication of dislocations and lattice distortions, together with the appearance of Moiré patterns.The Johnson-Cook(J-C) plasticity model is employed to research the constitutive relationship of the composites. And it can reasonably predict the plastic flows upon dynamic compression for the present composites.