Crystallization And Deformation Behavior Of Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ Metallic Glass

Bulk metallic glass have been developed in many alloy systems and show many unique properties associated with atomic structure, such as high yield strength, large elastic limit, corrosion resistance, and so on. Recently, development of Ti-based bulk metallic glass with lower density and higher specific strength is expected to expand the possible application fields. In this paper, the structural relaxation and crystallization behavior of Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ amorphous alloy, due to its higher glass forming ability and mechanical properties, are investagited by differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermal dilatometer and transmission electron microscopy (TEM). In addition, the compressive deformation and fracture mechanism of Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ bulk amorphous alloy over wider temperature region (77-621K) and strain rates are explored in detail.In the paper, the effects of relaxation and crystallization process on the stability of metallic glass in supercooled liquid region have been studied. Under continuous heating conditions, the activation energies for the glass transition and crystallization at the onset and first peak crystallization temperatures of Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ amorphous ribbons were 384, 228, 306 KJ/mol, respectively, which were higher than that in bulk metallic glass. The results indicated that the stability of metallic glass was strongly depended on the cooling rate in the glass transition process; the stability of amorphous ribbons was higher than bulk metallic glass.Crystallization kinetics research indicated that the glass transition and crystallization behavior showed the typical characteristic of kinetics. The crystallization process contained three steps of crystallization reactions corresponding to the precipitation of quasicrystalline phase on the amorphous maxtrix, the precipitation of Laves phase on the remaining amorphous maxtrix and the transition from quasicrystalline phase to Laves phase, the transition from Laves phase to an unknown phase, respectively. The average expansion coefficient was 9.89×10^-6K^-1 before crystallization, the reducing free volume led to the rapid decrease of the expansion coefficient in the crystallization process in Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ alloy.Share bands appeared at the outboad of the samples with a direction of normal and parallel to the fracture surface when tested at room tempareture and the compression...