Discovery of Critical Oxygen Content for Glass Formation in Zr_(80)Pt_(20) Melt Spun Ribbons

摘要

Zr_(80)Pt_(20) alloys may form meta-stable quasicrystals either during devitrification of an amorphous phase or directly upon cooling from a liquid depending on processing conditions. To date, little attention has been given to the role of oxygen on the glass formation or devitrification behavior of Zr-Pt and similar alloys. This study reveals that oxygen content during melt spinning indeed strongly influences the formation of the as-quenched structure. A critical amount of oxygen was found to be required to form amorphous ribbons at a fixed quench rate. At lower oxygen levels (i.e., <500 ppm mass), a fully crystallized is formed; the structure is composed mainly of meta-stable β-Zr with a small fraction of a quasicrystalline phase. At higher oxygen levels, the as-quenched structure transitions to a fully amorphous structure (～1000 ppm mass), and with further oxygen addition forms a mixture of amorphous and quasicrystalline (～1500 ppm mass) or crystalline phases (>2500 ppm mass). Details regarding the structure of the meta-stable β-Zr phase in the low-oxygen ribbons are provided along with a discussion of the structural similarity between this phase and the quasicrystal structure that formed in this alloy.