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The existence of liquid–liquid phase transitions has been suggested for liquid Fe and some of its alloys. In order to shed light on this phenomenon in-situ cooling of the Fe 80 B 20 and Fe melts was performed under a synchrotron beam radiation. It allowed for the continuous acquisition of X-ray diffraction spectra in the supercooled liquid region below the liquidus temperature. The procedure allowed monitoring of the structural changes in the supercooled liquid state using real-space atomic pair PDF(R) and radial RDF(R) distribution functions. The results are discussed in comparison with those of molecular dynamics simulation for liquid Fe. [ABSTRACT FROM AUTHOR]

Abstract: In situ vitrification in a synchrotron beam during cooling of a Pd42.5Cu30Ni7.5P20 melt allowed continuous acquisition of X-ray diffraction spectra in the supercooled liquid region between the liquidus temperature Tl and the glass transition temperature Tg for the first time in a metallic liquid alloy. These and subsequent acquisitions on reheating allowed determination of the structural changes in the supercooled and glassy states using the real space atomic pair distribution function PDF(R) and radial distribution function RDF(R). The nearest neighbor (NN) distance in the first coordination shell has a low R peak (pre-peak) that appears and increases on cooling from the liquidus temperature to the glass transition temperature in the supercooled liquid region. In this temperature range reversible expansion of the NN distances in the first coordination shell is observed. The slope of the expansion changes discontinuously at the glass transition. This behavior is explained by the theory of local topological fluctuations. [Copyright &y& Elsevier]

Abstract: Using cold graphite mold casting method, Al-based chill-zone alloys cylinders of millimeter scale thickness [Y. Li, K. Georgarakis, S.J. Pang, A. LeMoulec, T. Zhang, A.R. Yavari, unpublished research.] were prepared. Using high-resolution scanning electron microscopy (HRSEM), it was found that hard submicron crystalline surface layers of thickness about 200μm form when the melt can be undercooled. The structure and the thermal properties of the chill-zone alloy were examined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). A metastable phase Al19Ni5Y3 nucleated during cooling then transformed to equilibrium intermetallics after annealing. The chill-zone alloy shows high mechanical strength in excess of 1GPa at high ambient temperatures and good plasticity. The combination of high strength and good plasticity will be discussed in relation to the special structure of the chill-zone alloy. [Copyright &y& Elsevier]

Abstract: (Zr0.55Al0.1Ni0.05Cu0.3)99Y1 bulk metallic glasses heavily deformed by cold rolling were studied by X-ray diffraction (XRD) in transmission using high energy monochromatic synchrotron radiation during in situ heat treatment. No crystalline grain was detected in the cold-rolled samples. After deformation, excess free volume, ΔV f, was measured by X-ray diffraction. In situ heating XRD results revealed that metastable crystalline phase was nucleated and grew before the formation of equilibrium CuZr2. Further investigation showed that the metastable phase is Zr3Al2-type crystalline structure which is the primary crystalline phase that appears in several Zr-based metallic glasses during the thermal treatment [Plappert R, Boström M, Kühn U, Vaughan G, Yavari AR, Kvick Å. ISMANAM, Paris; 2005]. [Copyright &y& Elsevier]

Highlights: [•] A new orthorhombic phase of the intermetallic compound Ti3Sn was found. [•] A reversible orthorhombic-to-hexagonal transition into Ti3Sn was observed using XRD. [•] The unit cell and space group of orthorhombic phase are defined. [•] Crystallographic relations between orthorhombic and hexagonal phases are analyzed. [ABSTRACT FROM AUTHOR]