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(a) High-resolution transmission electron microscopy (Philips CM300 field emission gun TEM operating at ) image of melt-spun amorphous ribbon. Inset: corresponding electron diffraction pattern (CEDP) confirms that the alloy is entirely amorphous. (b) Low-magnification bright-field TEM plane-view image showing the spontaneous formation of a steady-state stripe patterned morphology comprising nanocrystalline phase through phase separation. Analytical average compositions (at. %) of dunelike for the melt-spun alloy annealed at were measured by EDX as Zr , Al , Ni , and Co in white (Zr depleted), and Zr , Al , Ni , and Co in gray region (Zr rich) in (c), respectively. Note that the composition measurement of the gray region includes a small part of the nanocrystal precipitation. Inset: CEDP of the as-annealed metallic alloy consists of duplex separate diffuse rings (or halos) and several almost continuous diffraction rings, indicating the coexistence of amorphous phase separation and nanocrystals. (c) High-magnification dark-field TEM image of (b). (d) High-resolution TEM image for the melt-spun alloy annealed at , showing the (511) (333) lattice fringes of a face-centered cubic intermetallic compounds nanocrystal precipitated in amorphous matrix. The main phase of alloy was identified using a unified phase with a cubic enhanced solid solution structure ( type) since they have the same cubic structure and approaching lattice parameter (i.e., for and for ). JCPDS files for (Ref. 26) and for (Ref. 27) were taken as references.
XRD patterns (with radiation, ) of the amorphous alloy ribbon at as quenched (a), and after heat treatment in vacuum of for (b), for (c), for (d), for (e). Arrow heads mark primary phases.
(top) Continuous DSC traces (2010, TA Instruments, well calibrated) of the melt-spun alloy in a flowing high purity argon atmosphere at different heating rate of (a) , (b) , (c) , and (d) , respectively. Inset: the melting process of the ingot on a high sensitive Setaram, Labsys™ TG-DSC16. (Bottom) The Avrami plot. Note that the open (the first time) and solid (the second time) marks represent the results of two individual different experiments, respectively. The dotted lines guide the eyes.
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