Browsing by Author "Shibayama, T"

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    Hidden amorphous phase and reentrant supercooled liquid in Pd-Ni-P metallic glasses
    (International Conference on Neutron Scattering, 2017-07-12) Lan, S; Ren, Y; Wei, X; Wang, B; Gilbert, EP; Shibayama, T; Watanabe, S; Ohnuma, M; Wang, XL
    An anomaly in differential scanning calorimetry has been reported in a number of metallic glass materials in which a broad exothermal peak was observed between the glass and crystallization temperatures. The mystery surrounding this calorimetric anomaly is epitomized by half century long studies of Pd-Ni-P metallic glasses, arguably the best glass-forming alloys [1]. Here we show,using a suite of in-situ experimental techniques, including simultaneous small-angle neutron scattering-calorimetry, high-energy X-ray diffraction, and electron microscopy, that Pd-Ni-P alloys have a hidden amorphous phase in the supercooled liquid region. The anomalous exothermal peak is the consequence of a polyamorphous phase transition between two supercooled liquids, involving a change in the packing of atomic clusters over medium-range length scales as large as 18Å. With further temperature increase,the alloy reenters the supercooled liquid phase which forms the room-temperature glass phase upon quenching. The outcome of this study raises a possibility to manipulate the structure and hence the stability of metallic glasses through heat-treatment.