In situ visualization of Ni–Nb bulk metallic glasses phase transition

Abstract

We report the results of in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior. The X-ray diffraction (XRD), transmission electron microscopy (TEM), nano-beam diffraction (NBD), differential scanning calorimetry (DSC), radial distribution function (RDF) and scanning probe microscopy/spectroscopy (STM/STS) techniques were applied to analyze the structure and electronic properties of Ni 63.5 Nb 36.5 glasses before and after crystallization. It was proved that partial surface crystallization of Ni 63.5 Nb 36.5 can occur at the temperature lower than that for the full sample crystallization. According to our STM measurements the primary crystallization originally starts with the Ni 3 Nb phase formation as a leading eutectic phase. It was shown that surface crystallization drastically differs from the bulk crystallization due to the possible surface reconstruction. The mechanism of Ni 63.5 Nb 36.5 glass alloy 2D-crystallization was suggested, which corresponds to the local metastable (3×3)− Ni(111) surface phase formation. The possibility of different surface nano-structures development by the annealing of the originally glassy alloy in ultra high vacuum at the temperature lower, than the crystallization temperature was shown. The increase of the mean square surface roughness parameter R q while moving from glassy to fully crystallized state can be caused by concurrent growth of Ni 3 Nb and Ni 6 Nb 7 bulk phases. The simple empirical model for the estimation of Ni 63.5 Nb 36.5 cluster size was suggested, and the obtained value (about 8 Å) is in good agreement with the STM measurements data (8 Å-10 Å).

Interatomic potential to predict the glass-forming ability of Ni–Nb–Mo ternary alloys

“…Besides the comparison with thermodynamics, experimental results are provided as well. One can find that in the Ni-Nb system, metallic glasses were obtained by IBM and rapid solidification (RS), while in the Ni-Mo system, amorphous alloys were synthesized by solid-state reaction (SSR) and mechanical alloying (MA) [12][13][14][49][50][51][52]. The compositions of the metallic glasses produced by these techniques were marked by red symbols in Fig.…”

Difference in charge transport properties of Ni-Nb thin films with native and artificial oxide

“…In addition, surface atomic structure of Ni-Nb bulk metallic glassy samples and their in-situ crystallization process were studied by scanning tunneling microscopy/ spectroscopy. 15,16 Oxidation may induce surface crystallization of the glassy matrix. 17,18 Fine-grained microstructure consisting of ZrO 2 and Cu particles was found at the surface of Zr 70 Cu 30 ribbons stored for a few years at room temperature 19 owing to surface oxidation.…”

Formation of nanostructured metallic glass thin films upon sputtering

“…Ni 62 Nb 38 target of 50 mm in diameter and 2 mm in thickness for sputtering machine was cut from a master alloy, prepared by arc melting of the mixture of pure elements (99.9% purity). This glassy alloy has a good glass forming ability GFA [ 22 , 23 ] and its atomic structure, crystallization [24] as well as surface oxidation behavior was carefully studied [25] . Thin films were prepared by magnetron radio frequency (RF) sputtering technique (TOEI SP-3003-33) with initial pressure inside the chamber of 10 −4 Pa without any special cooling techniques, though in some experiments the substrate was deliberately heated up.…”