Effect of oxygen on the thermal stability of Zr-Cu-Ni-Al-Ti bulk amorphous alloy

Crystal Zr bar and sponge Zr were employed as raw materials to prepare wedge-like specimens of Zr_52.5Cu_17.9 Ni_14.6Al₁₀Ti₅ bulk amorphous alloy with different oxygen impurity contents by a tilt casting method using ladle hearth type arc furnace. Effects of oxygen impurity on the alloy's glass forming ability and thermal stability were investigated. It is shown that the glass forming ability of the quinary alloy characterized by maximum amorphous sample forming thickness t_max was decreased as oxygen impurity content increased, on the contrary, its thermal stability characterized by supercooled liquid region ΔT_x1 was enhanced. Oxygen impurity has the tendency to heighten the apparent activation energy E_ax1 for the crystallization process onset of the amorphous alloy, which made the crystallization incubation period of the alloy under larger supercooled state lengthened and thereby the thermal stability enhanced.