Solidification Atmosphere and Glass-Forming Ability of Engineering Important Fe- and Zr-Based Bulk Glassy Alloys

It is important to clarify the best solidification condition for the formation of bulk glassy alloys in Fe- and Zr-based alloy systems with engineering values. The effectiveness of atmosphere during injection casting changes in the order of O2 > Air > N2 > Ar > He for Fe76Si9B10P5 bulk glassy alloy and 105 Pa He > 105 Pa Ar > 103 Pa Ar > vacuum for Zr65Al7.5Ni10Cu17.5−xPdx (x = 0–17.5 %) bulk glassy alloys. The effectiveness of oxygen atmosphere is due to the suppression of crystal nucleation rate caused by the increase in surface tension of liquid by the dissolution of oxygen in case of Fe-based alloy. In case of Zr-based bulk glassy alloys, the He atmosphere is effective due to the maintenance of cleanness of alloy liquid as well as the increase in the cooling rate. The opposite tendency of the effectiveness for helium atmosphere in the same injection casting is important for further development of the production techniques for large-scale Fe- and Zr-based bulk glassy alloys.