Formation and Mechanical Properties of Bulk Glassy Ni_57-xTi₂₃Zr₁₅Si₅Pd_x Alloys

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The glass-forming ability in Ni_57−xTi₂₃Zr₁₅Si₅Pd_x (x=0, 5, 10, 12.5, 15 and 20) alloys as a function of Pd concentration was examined by melt-spinning and copper mold casting methods. All the melt-spun ribbons are in a glassy state. ΔT_x(ΔT_x=T_x−T_g) and T_g⁄T_m were used to evaluate the glass-forming ability, where T_g,T_x and T_m represent the glass transition, crystallization and melting temperatures, respectively. The observation of large ΔT_x and T_g⁄T_m values in the 12.5 at%Pd alloy implies a high glass-forming ability. At this composition, a cylindrical bulk alloy with a diameter of 2 mm was verified to be in a single glassy state. For the bulk cylinder of 3 mm in diameter, the volume fraction of glassy phase is approximately 92%. The compression fracture strength (σ) and Vickers hardness (H_v) of the bulk glassy alloy are 2100 MPa and 620, respectively. These results demonstrate the good mechanical performance of the present Ni-based bulk glassy alloy, which is prominent for future application.