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.

Room temperature fast-ion conduction in imidazolium halide salts

Fast-ion conduction has been observed in the iodide and bromide salts of 1-methyl-3-ethylimidazolium at ambient temperatures. The melting point of these two compounds is above 350 K and even at 273 K the ionic conductivity in the solid-state is greater than 10⁻³S cm⁻¹. Cation diffusion coefficients have been measured using fringe field gradient and/or pulse field gradient ¹H NMR techniques, which indicated cation diffusion coefficients of the order of 10⁻¹⁰ m² s⁻¹ in the solid-state. Remarkably, these values are up to an order of magnitude higher than the cation diffusion coefficient in the supercooled liquid at 293 K. The activation energy for diffusion in the solid-state is extremely small, as is typical of solid-state fast-ion conductors and indicates a change in transport mechanism from the melt to the crystal. The inability to detect an ¹²⁷I signal together with the modelling of the conductivity using the Nernst–Einstein equation suggests that the solid-state conduction is primarily due to cation diffusion. The solid-state fast-ion conduction is most likely related to vacancy diffusion along the cation layers in the crystal. The temperature dependence of the NMR signal intensity indicates that the number of mobile species is increasing with increasing temperature with an activation energy of approximately 20–30 kJ mol⁻¹.

Thermal stability of the Al70Ni10Ti10Zr5Ta5 amorphous alloy powder fabricated by mechanical alloying

An Al₇₀Ni₁₀Ti₁₀Zr₅Ta₅ amorphous alloy powder was fabricated by mechanical alloying. The phase structure and characteristic temperatures of the alloy were determined by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The glass transition behavior and crystallization kinetics were analyzed using Lasocka and Kissinger functions. The results show that the alloy has a higher crystallization temperature, a higher effective activation energy of crystallization and a wider supercooled liquid region than the previously reported values, suggesting a high thermal stability and promising applications.