Discovery of Critical Oxygen Content for Glass Formation in Zr 80 Pt 20 Melt Spun Ribbons

Zr80Pt20 alloys may form meta-stable quasicrystals either during devifxification 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., 4 0 0 ppm mass), a fully crystallized is formed; the structure is composed mainly of metastable p-Zr with a small fiaction of a quasicrystalline phase. At higher oxygen levels, the asquenched structure transitions to a hlly amorphous structure (-1000 pprn mass), and with further oxygen addition forms a mixture of amorphous and quasicrystalline (-1500 ppm mass) or crystalline phases (>2500 pprn mass). Details regarding the structure of the meta-stable p-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.