Liquid ejection temperature dependence of structure and glass transition behavior for rapidly solidified Zr-Al-M (M=Ni, Cu or Co) ternary glassy alloys

Abstract

The appearance/disappearance of glass transition (GT) and supercooled liquid (SL) region was found to be affected for Zr-Al-(Ni, Cu, Co) glassy ribbons by changing the ejection temperature (Te) in the range from liquid temperature (Tl)+200 K (LT) to Tl+700 K (HT). The Te at which the disappearance occurs lies around 600–700 K above Tl. The oxygen contents increase from 240 to 550 ppm for LT samples to 990–4440 ppm for HT samples, but their contents are lower than those (4000–5000 ppm) for the samples with GT and SL region. The AES analyses show that the oxygen was segregated to the thin surface region. As compared with LT samples, HT samples exhibit higher hardness and glass transition temperature (Tg), while keep good bending ductility. Structure analyses using high energy X-ray diffraction and MD simulations show the change to looser atomic configurations for HT sample. The disappearance of GT for HT samples reflects the change of liquid structure from icosahedral-like medium-range ordered structure to a less-coordinated atomic structure. The GT appears again by ejection after the lowering of Te from Tl+700 K to Tl+300 K. The Te dependence of GT together with the changes in Tg and hardness is encouraging for novel material science/engineering field through the control of liquid structures.