Influence of oxygen content in phase selection during quenching of Zr80Pt20 melt spun ribbons

Depending on processing conditions Zr80Pt20 alloys may form meta-stable quasicrystals either during devitrification of an amorphous phase or directly upon cooling from a liquid. This study reveals that oxygen content during melt spinning indeed strongly influences the formation of the as-quenched structure in this alloy system. At a wheel speed of 25 m/s, a critical amount of oxygen was found to be required to form amorphous ribbons. At lower oxygen levels (i.e. <500 ppm mass), a fully crystallized structure forms that is composed mainly of meta-stable β-Zr with a small fraction of a quasicrystals (QC) phase. At higher oxygen levels (∼1000 ppm mass), the as-quenched structure transitions to an apparently amorphous structure, and with further oxygen additions forms a mixture of amorphous and either a QC phase (∼1500 ppm mass) or a crystalline Zr6Pt3O phase (>2500 ppm mass). Details regarding the structural similarity between the QC, β-Zr and Zr6Pt3O phases are discussed.