Effects of quenching rate on amorphous structures of Cu46Zr54 metallic glass

Metallic glass shows some superior properties different from crystalline, but the nature of amorphous structure and structural change during glass transition have not been completely understood yet. Molecular dynamics simulation provides intuitive insight into the microstructure and properties at atomistic level. Before probing into the microstructures of metallic glass with molecular dynamics (MD) simulation, it is important to obtain amorphous state first. In the current work, we reproduce the process of manufacturing metallic glass in laboratory including the melting, equilibrating and quenching procedure with molecular dynamics simulations. The structure changing at melting point and glass transition temperature are investigated with the different cooling processing. The partial radial distribution function (PRDF) is applied as a criterion to judge the final amorphous state obtained considering the quenching at different cooling rates and the effects of cooling rate on the formation of amorphous structures are further discussed.

Mg-based metallic glass / titanium interpenetrating phase composite with high mechanical performance

We report an Mg-based metallic glass/titanium interpenetrating phase composite in which constituent phases form a homogeneously interconnected network. The porous titanium constrains shear bands propagation thoroughly and promotes shear bands branching and intersection subsequently. The homogeneous phase distribution promotes regularly distributed local shear deformation and leads to a uniform deformation for the composites. Moreover, the interpenetrating phase structure introduces a mutual-reinforcement between metallic glass and titanium. Therefore, the composite exhibits excellent mechanical performance with compressive fracture strength of 1783 MPa and fracture strain of 31%.

Extrusion properties of a Zr-based bulk metallic glass

The extrusion behavior of Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 metallic glasses in the supercooled liquid region was investigated. Good extrusion formability was observed under low strain rates at temperatures higher than 395 °C. The metallic glasses were fully extruded without crystallization and failure within the range of T=395–415 °C under strain rates from 5×10⁻³ s⁻¹ to 5×10⁻² s⁻¹, and the deformation behavior of the metallic glasses during the extrusion was found to be in a Newtonian viscous flow mode by a strain rate sensitivity of 1.0.

Preparation and characterisation of metallic glassy/amorphous materials

This thesis studied the plastic deformation behaviour of bulk metallic glasses by conducting indentations on various thermal histories using bonded interface technique. Another effort was to probe the route to fabricate bulk amorphous alloy via consolidating amorphous powder.

Surface modification of biocompatible metallic materials for bone tissue engineering

Titanium, zirconium and TiZr binary alloy were fabricated using a powder metallurgical method. Appropriate surface modifying techniques were conducted on the metals to render an ability for apatite formation. Their biocompatibility has also been assessed. These materials showed potential for biomedical applications because of their excellent bioactivity and biocompatibility which may improve bonding of the implants to juxtaposed bone.

Identification and quantification of cholesterol oxides in foods

The types and levels of nine major cholesterol oxidation products was determined in a variety of foods. An estimate was made of the possible levels of cholesterol oxides in the Australian diet. These levels have been shown to cause endothelial damage in the coronary arteries of laboratory animals in previous studies. The health implications of these observations to humans is unknown.

Theoretical study on behaviour of superplastic forming/diffusion bonding of bulk metallic glasses

Based on the behaviour of the superplastic deformation of metallic glasses and Pilling’s model, a diffusion bonding model suitable for metallic glasses is proposed in the present study. In the current model, the diffusion bonding processes consists of two stages: one is the plastic deformation stage and the other is the void shrinkage stage, in which, the atom diffusion and superplastic deformation are responsible for the void shrinkage. Applying this model to the diffusion bonding of a Zr based metallic glass, the predicted bonding time is in good agreement with the experimental result. A map for determining the bonding temperature and time to achieve high quality bonding in a Zr based metallic glass is suggested.

Compressive deformation and damage of Mg-based metallic glass interpenetrating phase composite containing 30-70 vol% titanium

Mg-based metallic glass interpenetrating phase composites (IPCs) containing 30-70 vol% titanium was fabricated in this study. The effects of reinforced phase volume fraction and interspace on the mechanical properties were investigated systematically. With increasing the volume fraction of titanium, the fracture strength and strain increased up to 1860 MPa and 44%, respectively. The results showed that the critical volume fraction (around 40%) of Ti metal should be required for significantly improving plasticity of IPC. Decreasing the interspace of the titanium phase could lead to enhancement of yield and fracture strength. The deformation behavior and strengthening mechanisms were discussed in detail.

Nanograin metals and metallic multilayers produced by severe plastic deformation

This research has developed an improved understanding of the structure-property relationships, fabrication technology and deformation mechanism of light bulk ultrafine grained materials and metallic multilayered structure.

Integrated fluid-thermal-structural numerical analysis for the quenching of metallic components

The quenching of a metal component with a channel section in a water tank is numerically simulated. Computational fluid dynamics (CFD) is used to model the multiphase flow and the heat transfer in film boiling, nucleate boiling and convective cooling processes to calculate the difference in heat transfer rate around the component and then combining with the thermal simulation and structure analysis of the component to study the effect of heat transfer rate on the distortion of the U-channel component. A model is also established to calculate the residual stress produced by quenching. The coupling fluid-thermal-structural simulation provides an insight into the deformation of the component and can be used to perform parameter analysis to reduce the distortion of the component. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg.

Oxygen reduction reaction activity and structure of La-based perovskite oxides

1706 files in 35 folders, containing 388MB. Comprises plots, figures, and manuscripts. The data contains x-ray diffraction patterns and electrochemical data of lanthanum based perovskite oxides (e.g. 9 different perovskite compositions e.g. LaNiO₃, LaCoO₃, LaFeO₃, LaMnO₃, LaCrO₃, LaNi_0.5Co_0.5O₃ and LaNi_0.5Fe_0.5O₃, LaNi_0.5Mn_0.5O₃ and LaNi_0.5Cr_0.5O₃) characterized using rotating ring disk electrodes.

Synthesis of high surface area amorphous tin-zinc oxides by a sol-gel method

A new method to synthesize conducting oxide nanoparticles with low photocatalytic activity was investigated. Initially, the preparation of amorphous ZnO-SnO2 solid solution nanoparticles was studied using a sol-gel technique. It was found that X-ray amorphous nanopowders with low photocatalytic activity were produced when the precipitates were heat treated below 500 °C. However, FT-IR data showed that the sample may not be an oxide semiconductor. A mixture of ZnO and SnO2 crystalline nanoparticles was also produced at 800 °C and found to have much reduced photoactivity than commercial ZnO nanoparticles having a similar specific surface area.