Synthesis of bulk metallic glass in the Ti-rich part of the Ti-Cu-Ni-Sn-Be-Zr alloy system

The glass forming ability and crystallization behaviour of melt spun Ti_50-xCu₂₅ Ni₁₅Sn₃Be₇Zr_x (x = 0, 3 and 5) amorphous alloys were investigated using differential scanning calorimetry (DSC), X-ray diffractometry and transmission electron microscopy. With increasing Zr contents, x from 0 to 5, ? T_x (= T_x - T_g) and T_rg(= T_g/T_l), where T_g=glass transition temperature, T_x=crystallization temperature and T_l=liquidus temperature, gradually increase from 45 K to 56 K and from 0.57 to 0.60, respectively. The Ti₅₀Cu₂₅Ni₁₅Sn₃Be₇ alloy shows three exothermic events in the DSC curve; initially the alloy crystallizes by forming a few nanometer scale crystalline phase, followed by decomposition into a mixture of Ti(Ni,Cu), TiCu, Ti₃Sn, and TiBe₁₂ phases at high temperature. Furthermore, the alloys containing Zr exhibit the formation of nanocrystalline phases of ∼10 nm size even after the second exothermic event due to their increased atomic packing density. For the Ti₄₅Cu₂₅ Ni₁₅Sn₃Be₇Zr₅ alloy, fully amorphous rods up to 5 mm in diameter were successfully fabricated by injection casting.