Influence of oxygen contents on nanocrystallization of Co33Zr67 and Zr65Cu17.5Ni10Al7.5 alloys

C0(33)Zr(67) ribbons with increasing oxygen contents were produced by melt-spinning. Crystallizing phases were compared with the stable phases in the relevant part of the ternary system Co-Zr-O. Our results indicate that even minor oxygen contents lead to drastic changes in the crystallization mode and kinetics, i.e. the formation of nanocrystalline microstructures instead of large grained CoZr2. It is assumed that the dramatic change in the nucleation behaviour results from phase separation in the Co-Zr-O glasses. The nanocrystalline phase formed is always the so-called ''big-cube phase'' (E9(3), fcc: a approximate to 1.22 nm). Zr65Cu17.5N10Al7.5 ribbons without and with 1.5 at.% oxygen were produced by melt-spinning. Whereas in oxygen-free samples primary crystallization of a quasicrystalline phase was observed, crystallization of oxygenated glasses leads to additional formation of a nanocrystalline fee phase with the same structure as known from the binary Zr-based glasses.