Showing papers by "Mingwei Chen published in 1999"
Abstract: A quasicrystalline phase was discovered in a Zr65Al7.5Ni10Cu12.5Ag5 bulk metallic glass annealed in the supercooled liquid range. Through systematical transmission electron microscopy rotation analyses, the selected area electron diffraction patterns are obtained corresponding to fivefold, threefold, and twofold rotational symmetry, demonstrating that the precipitated phase is an icosahedral quasicrystalline phase with good rotational symmetry. It is concluded that the addition of Ag in the Zr-based metallic glass promotes the formation of the quasicrystalline phase. The present experimental result implies that there is a natural relationship between the Zr-based bulk metallic glasses and icosahedral quasicrystalline.
189 citations
TL;DR: In this paper, the formation of icosahedral phase from the rapidly quenched Zr65Cu7.5Al7.10 metallic glass was confirmed and the kinetics of the precipitation upon isothermal annealing in the supercooled liquid region were examined by differential scanning calorimetry.
Abstract: The formation of an icosahedral phase from the rapidly quenched Zr65Cu7.5Al7.5Ni10Ag10 metallic glass was confirmed and the kinetics of the precipitation upon isothermal annealing in the supercooled liquid region were examined by differential scanning calorimetry. Based on the kinetic analysis, it is clarified that the precipitation in the supercooled liquid region takes place by an interfacial controlled growth with a nearly steady-state nucleation rate. The Arrhenius plot between effective time lag, τ, of nucleation and isothermal annealing temperature yields a single linear relation, in which the activation energy for nucleation is evaluated to be 366 kJ/mol. It is concluded that the transformation of amorphous to quasicrystal proceeds by a homogeneous nucleation mode, which is different from those of Pd–U–Si and Al–Cu–V quasicrystals arising from an inhomogeneous distribution of quenched-in nuclei.
80 citations
TL;DR: In this article, atom probe results on impurity oxygen dissolution in a Zr65Cu15Al10Pd10 metallic glass and its redistribution during nanocrystallization were reported.
Abstract: We report atom probe results on impurity oxygen dissolution in a Zr65Cu15Al10Pd10 metallic glass and its redistribution during nanocrystallization. Approximately 0.1 at. % impurity oxygen is detected from the as-melt-spun Zr65Cu15Al10Pd10 metallic glass. Oxygen redistribution occurs during annealing. In some crystallites, oxygen up to 4 at. % is detected, and virtually no oxygen is dissolved in the remaining amorphous phase. This result directly demonstrates that impurity oxygen promotes the crystallization by forming metastable phases containing high content oxygen and thereby influences the kinetics of crystallization.
43 citations
TL;DR: In this article, a crack propagates along the interfaces between nanocrystals and the amorphous matrix in the alloy with optimized microstructures combining with macromechanical properties.
Abstract: Fracture surfaces of a nanocrystallized Zr65Cu15Al10Pd10 metallic glass were observed on an atomic scale with field ion microscopy Based on geometrical and phase characteristics of the fracture morphologies, it can be determined that a crack propagates along the interfaces between nanocrystals and the amorphous matrix in the alloy with optimized microstructures Combining with macromechanical properties, it is proposed that the strengthening effect of nanocrystals in the Zr-based metallic glass arises from a strong interaction between nanocrystals and local shear bands during deformation processes of the glassy matrix
20 citations