Low temperature dynamic compression properties of Ti₄₀Zr₂₅Ni₈ Cu₉Be₁₈ bulk amorphous alloy

The Ti₄₀Zr₂₅Ni₈ Cu₉Be₁₈ bulk amorphous alloy was prepared by copper mould casting. The dynamic compression properties of the alloy was investigated with the split Hopkinson pressure bar (SHPB) under high strain rates at room temperature (25°C) and liquid nitrogen temperature (-196°C). The fracture was characterized by the S-4800 scanning electron microscope. The results show that the Ti₄₀ Zr₂₅ Ni₈ Cu₉ Be₁₈ alloy presented similar dynamic compression strengths at different strain rates, revealing a negative strain hardening effect at room temperature. In contrast, a significantly increased dynamic compression strength was observed under a larger strain rate at liquid nitrogen temperature. Obviously such a low temperature led to strain hardening. A shear fracture happened when the Ti₄₀Zr₂₅Ni₈ Cu₉Be₁₈ alloy was compressed at room temperature, evidenced by the observed vein pattern and shear bands. The shear bands induced the formation and propagation of cracks. The fracture exhibited cleavage steps and a river pattern for the alloy deformed at liquid nitrogen temperature. Though the dynamic fracture proceeded, the local strain concentration contributed to the plastic deformation at room temperature. The kinetic energy was largely transformed to heat which was offset at liquid nitrogen temperature, weakening the adiabatic shearing action.