应用同步辐射小角x射线散射和差示扫描量热分析对块体非Zr55 Cu30 Al10 Ni5晶合金结构弛豫进行了研究实验结果表明：经340℃、不同时司退火后的非晶内部的电子密度涨落随退火时司的延长先增大而后减小；玻璃转变温度附近焓弛豫峰的表观激活能则随退火时司的延长先减小而后增大结果反映了随退火时司的延长，块体非晶台金内部类液体区不断减少及类固体区不断增加的过程

The oxidation behavior of Zr55 Cu30 Al10 Ni5 bulk metallic glass in air in the glassy state and the supercooled liquid state was studied using a thermogravimetric analyzer, X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Itwas found that the isothermal oxidation kinetics of the glass in both states follows a two-step parabolic law. The oxidation process is governed by the inward diffusion of oxygen and the outward diffusion of Cu, with the first being dominant. The faster diffusion of atoms in the supercooled liquid state led to a network precipitation of crystalline Cu, and the crystallization that occurred in this state in the later stage of oxidation caused a reduction in the rate of oxidation. Two types of Zr oxides, i.e. t-ZrO2 and m-ZrO2, were formed in the oxidation process in both the glassy and supercooled liquid states. t-ZrO2 mainly formed in the outer layer of the oxide scale, while m-ZrO2 tended to form in the inner layer. The formation of m-ZrO2 is possibly activated by the crystallization of the glass near the interface of the oxide scale and the substrate alloy. In addition, oxidation also has a substantial effect on the formation of crystallized phases. The formation of a Cu-rich phase of Cu10Zr7 occurred in the oxidizing atmosphere. However, the formation of a Zr-rich phase of Zr2(Ni, Cu) mainly took place in a vacuum environment.

Academy of Sciences, 100039 Beijing, People's Republic of China In this paper, positron annihilation spectroscopy and differential scanning calorimetry were applied to study the structural relaxation of Pd40 Cu30 Ni10 P20 bulk metallic glass during long-time annealing at 523K. It was found that the relaxation of the alloy follows a two-stage process. In the initial stage, with increasing annealing time, the height of the glass transition peak (namely cp) increased, while the average positron lifetime decreased. The isothermal relaxation kinetics obeys a Kohlrausch law with exponent of β=0.5±0.03. However, when the annealing time is beyond 32 h, the height of the glass transition peak (cp) decreased, and the average positron lifetime increased. This is possibly due to the enhancement of the topological short-range ordering, which results in the generation of new defects on the interfaces between the solid-like regions and the liquid-like regions in amorphous phase. The experimental results were tentatively discussed in terms of free-volume theory and percolation theory.

Zr65 Ni10 Cu7.5 Al7.5 Ag10 bulk metallic glass was prepared by copper-mould casting. The kinetics and structure related to the phase transformation of the bulk metallic glass were studied by X-ray diffraction, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). It was found that the Zr65 Ni10 Cu7.5 Al7.5 Ag10 bulk metallic glass exhibits a distinct glass transition followed by twoexothermic reactions, with the first reaction being the amorphous-to-quasicrystalline transformation, and the second being the quasicrystalline-to-Zr2 Cu intermetallic transformation. The isothermal kinetics for amorphous-to-quasicrystalline transformation was quantitatively analyzed in the framework of JMA equation. The parameter of local Avrami exponent was introduced to explain the details of nucleation and growth behaviour in the transformation. It was revealed that the local Avrami exponent for the transformation varied with an increase in the volume fraction transformed, indicating that multi-mechanisms were involved in the transformation. TEM observations demonstrated that the variation in transformation kinetics at different stages is most likely the result of the structural inhomogeneity in the as-cast bulk metallic glass caused by a temperature gradient along the radius direction during casting. q 2004 Elsevier Ltd. All rights reserved.

The amorphous Zr64 Ni36, Zr60 Ni25 Al15, Zr65 Ni10 Cu17.5 Al7.5, and Zr63 Ni10 Cu17.5 Al7.5 C2 alloys were successfully synthesized by mechanical alloying of pure element powders. The structural evaluation of powder mixtures in the process of milling was monitored by X-ray diffraction and scanning electron microscopy. The thermal stability of the amorphous alloys obtained and the compositional effects on the glass forming ability were analyzed by differential scanning calorimetry. It was found that, except for Zr64 Ni36, other three amorphous alloys exhibit a distinct glass transition and wide supercooled liquid region ranging from 63 to 82℃. The amorphous Zr60 Ni25 Al15 alloy exhibits the highest glass transition and crystallization temperatures, while the amorphous Zr63 Ni10 Cu17.5 Al7.5 C2 phase shows the largest supercooled liquid region. The results demonstrate that addition of appropriate amounts of C extends the supercooled liquid region of Zr-Ni-based amorphous alloys. The effect of the C addition on the glassforming ability of Zr-Ni-based systems is discussed.