The microstructures and free-volume evolutions of as-cast and pre-annealed Zr65Al7.5Ni10Cu12.5Ag5 bulk metallic glasses during rolling deformation have been investigated. No phase transformation is detected in the as-cast/rolled specimen. However,the structural stability of the glass against plastic deformation is worse after pre-annealing,indicated by nanocrystallization in preannealed/rolled specimens with large deformation degrees. Moreover,with increasing deformation degree,the free-volume content in a pre-annealed/rolled specimen increases at a lower average rate than that in an as-cast/rolled specimen.
ZHOU Wei LU BinFeng KONG LingTi LI JinFu ZHOU YaoHe
Curing behaviors of the unsaturated polyester resin （UPR） containing 1-1.8 wt% methyl ethyl ketone peroxide （MEKP） initia- tor are investigated. The viscosity, gelation and vitrification transition of the UPR-MEKP systems are examined using the ro- tating viscometer and differential scanning calorimetry （DSC）. A liquid fragility parameter, Me, defined as the viscosity varia- tion rate of the liquids towards the curing temperature is presented. It is found that Mc has a good negative relation with the glass transition temperature （Tg） in the systems. Mc can be used for predicting the stability of the cured amorphous systems. The relationship between the liquid and cured thermoset polymer systems is studied from both the thermodynamic and kinetic point of view.
Similar element substitution has been applied for improving glass forming ability （GFA） in AI86NigLa5 amor- phous alloy. The effects of La-Ce and Ni-Co pairs on the GFA, magnetic properties and hardness of Al-Ni-La alloy were investigated by using X-ray diffraction （XRD）, transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, magnetometer and hardness-tester. The results show the GFA of the samples in the order of Al86（Ni0.5Co0.5）9（La0.5Ce0.5）5〈 A186Ni9Las〈A186Ni9（La0.5Ce0.5）5, implying that similar element substitution has a limited enhancing effect on the GFA of the present Al-Ni-La alloy. In addition, the measured samples display a diamagnetic behavior at room temperature. The variations of diamagnetic behavior as well as the microhardness of the samples are strongly dependent on the microstructure, i.e., the amounts of the icosahedral structure and precipitates, after the similar element substitution in the Al-Ni-La alloy.
Guihua Li Weimin Wang Xiufang Bian Li Wang Jiteng Zhang Rui Li Tao Huang
The formation and evolution characteristics of bcc phase during the isothermal relaxation processes for supercooled-liquid and amorphous Pb were investigated by molecular dynamics simulation and cluster-type index method （CTIM）. It is found that during the relaxation process, the formation and evolution of bcc phase are closely dependent on the initial temperature and structure. During the simulation time scale, when the initial temperature is in the range of supercooled liquid region, the bcc phase can be formed and kept a long time; while it is in the range of glassy region, the bcc phase can be formed at first and then partially transformed into hcp phase; when it decreases to the lower one, the hcp and fcc phases can be directly transformed from the glassy structure without undergoing the metastable bcc phase. The Ostwald＇s ＂step rule＂ is impactful during the isothermal relaxation process of the supercooled and glassy Pb, and the metastable bcc phase plays an important role in the precursor of crystallization.
A larger-scale Mg70Zn30 alloy system including 100000 atoms has been simulated by using the molecular dynamics method to investigate the icosahedral medium-range order （IMRO） formed in the MgToZn30 metallic glass. It is found that the simulated pair distribution function of Mg70Zn30 metallic glass is in good agreement with the experimental results. The glass transition temperature Tg is near 450 K under the cooling rate of 1×10^12 K/s. The icosahedral local structures play a critical role in the formation of metallic glass, and they are the dominant local configurations in the Mg70Zn30 metallic glass. The IMRO in the Mg70Zn30 metallic glass is characterized by certain types of extended icosahedral clusters combined by intercross-sharing atoms in the form of chains or dendrites. The size distributions of these IMRO clusters present a magic number sequence of 19, 23, 25, 27, 29, 31, 33, 35, 37, 39,..., and the magic clusters can be classified into three types according to their compactness. The IMRO clusters grow rapidly in a low-dimensional way with cooling, but this growth is limited near Tg.
The amorphous Fe78Si9B13 alloy was used as a heterogeneous Fenton catalyst in the process of phenol degradation.The influences of main operating parameters such as reaction temperature,catalyst amount,hydrogen peroxide dosage and initial pH of solution on phenol degradation rate were investigated.The maximum mineralization of phenol was achieved at 60°C,6 g/L Fe78Si9B13, 0.31 mol/L hydrogen peroxide,with an initial pH of 2.5.More than 99%of phenol was completely removed under the optimum conditions within 10 min for a solution containing 1000 mg/L of phenol.Batch experiments for solutions containing phenol con- centrations ranging from 50 to 2000 mg/L were investigated under the above conditions and the same excellent degradation rate was obtained.The Fe78Si9B13 showed better catalytic activity than iron powder and Fe 2+ .Addition of n-butannol(hydroxyl radical scavenger)decreased the degradation rate of phenol,which demonstrates that hydroxyl radicals were mainly responsible for the removal of phenol.We demonstrated that phenol may be degraded by hydroxyl radicals decomposed by hydrogen peroxide on the surface of Fe78Si9B13 and illustrated the reaction mechanism for this process.This amorphous alloy exhibited high stability in recycling experiments and showed excellent reuse performance even after continuous operations of 8 cycles.
To study the influence of Fe addition on the Al-based amorphous alloys,the structure and properties of Al84Ni10La6 and Al84Ni9Fe1La6 alloys were investigated through various techniques.The results show that 1% Fe（molar fraction） addition increases the area of the pre-peak in the structure factor and decreases the thermal expansion coefficient difference between the crystalline and amorphous states.1% Fe addition also improves the glass forming ability（GFA）,micro-hardness,fracture toughness,electric resistivity,absolute diamagnetism and corrosion resistance of Al-Ni-La alloys,which is related to the changes of medium-range order and quench-in free volume caused by 1% Fe addition.
