Pure mode II dynamic fracture characteristics and failure mechanism of Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 bulk metallic glass

Due to the amorphous nature of bulk metallic glasses (BMGs), the fracture mechanism of such materials is quite different from that of their crystalline counterparts. By far, how to obtain mode II dynamic fracture properties and reveal failure mechanism of BMGs remains an important issue to resolve. In this work, a novel experimental technique is adopted to determine pure mode II dynamic fracture toughness (DFT) of Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 BMG under high loading rates. The variations of fracture toughness, failure modes, and micromechanism of the material are investigated under different loading rates. The results show that under the current loading conditions, the loading rate is precisely controlled between 2.03 × 10⁶ MPa ⋅ m^1/2/s and 7.17 × 10⁶ MPa ⋅ m^1/2/s. The fracture initiation time t_f decreases with the increase of loading rates, but the mode II DFT is insensitive to the change of loading rates. According to different failure morphologies and fracture modes, the fracture surface exhibits three characteristic regions, where the corresponding micromechanism is analyzed in detail. From zone A to zone B, there exists an evolution of the fracture modes from brittle to ductile, and then to thermal-softening controlled fracture type. In zone C, due to the influence of the stress state at the crack tip, the component of mode I fracture set in, and the fracture path shows deflections from the main shear plane.