Microstructural characterization of Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass

The Zr46.8Ti8.2Cu7.5Ni10Be27.5 (V4) glass is one of the most stable metallic bulk glasses. It can be produced from the liquid melt at low cooling rates-down to 1 K/s. The crystallization sequence and the structure of the crystalline phases which form during annealing of this bulk glass were investigated by X-ray diffraction, by transmission electron microscopy and by three dimensional atom probing. After 42 d annealing time at 573 K small variations in contrast images were observed in TEM but no Bragg peaks. Whereas the glass in the as quenched state is chemically homogeneous, atom probe investigations of the annealed glass show a non-homogeneous distribution of the alloying elements. Significant non-random concentration fluctuations of Zr, Be and Ti were observed for this state with predominant wave lengths of about 35 rim, 25 nm and 40 nm, respectively. The amplitude of these concentration fluctuations was estimated for Zr as approximate to 5.8 at. %, for Be as approximate to 3.0 at. %, and for Ti as approximate to 1.6 at. %. After heating of the pre-annealed glass in a DSC apparatus with 4 K/min up to 709 K, which corresponds to a heat release of 4% of the first crystallization peak, nanosized crystals were found which were identified as quasicrystals.