Origin of the effect of the gas atmosphere during mold-casting Zr ₆₅Al _7.5Ni ₁₀Pd _17.5 bulk glassy or nano-quasicrystal-forming alloy

We provide a quantitative analysis of the importance of the gas species and pressure during mold-casting process on the apparent glass-forming ability (GFA) of Zr ₆₅Al _7.5Ni ₁₀Pd _17.5 alloy, recently reported by Kato et al. (e.g. Scripta Mater. 51 (2004) 13). The cooling characteristics are found to depend in remarkable detail on the gas species and the pressure existing in the cavity between the melt and the mold presumably formed during the cooling process. This understanding has been successfully applied to significantly improve the critical diameter of the glassy rods to 7 mm in an atmosphere of helium environment from 5 mm in that of argon.