Hongwang Zhang

Bulk metallic glass formation of Cu-Zr-Ti-Sn alloys

Cu-Zr-Ti-Sn bulk metallic glasses were produced by copper mold casting. The effects of Sn addition on glass-forming ability (GFA), thermal stability of the Cu60Zr30Ti10 bulk metallic glass were investigated. It was found that a bulk metallic glass of 5 mm in diameter was prepared in a (Cu60Zr30Ti10)(99)Sn-1 alloy by copper mold casting. The addition of 1 at.% Sn is effective for an increase in GFA. The DeltaT(x) and T-g/T-I are 46 K and 0.63, respectively, for (Cu60Zr30Ti10)(99)Sn-1 alloy. With increasing the content of Sn, the value of TITI increases, but the alloys begin to lose bulk metallic GFA. The new parameter gamma has a better correlation with the GFA of the Cu-based alloys

Preparation and hydriding/dehydriding properties of mechanically milled Mg-30 wt% TiMn1.5 composite

Abstract A Mg–30 wt% TiMn 1.5 hydrogen storage composite was successfully synthesized by mechanical milling of a mixture of magnesium powder and amorphous TiMn 1.5 powder. The absorption/desorption rates and storage capacity under different temperatures were evaluated. The composite possesses high hydrogen storage capacity and exhibits excellent absorption/desorption kinetic properties and is activated in situ due to reaction ball milling (RBM). The hydrogen capacity is over 2.7 wt% at 373 K, and one absorption/desorption hydrogen cycle can be finished in 20 min at 523–573 K. Interestingly, the desorption temperature begins at about 500 K, decreasing about 40 K in contrast to that of the milled pure MgH 2 . Mechanical milling produces fine powder with nanometer-scaled grains and introduces many imperfections into the Mg matrix, which contribute to the enhanced hydrogen absorption/desorption rates with high capacity catalyzed by TiMn 1.5 (amorphous).

Evaluation of Stored Energy from Microstructure of Multi-component Nanostructured Cu

A polycrystalline Cu of 99.995% purity has been deformed by dynamic plastic deformation at liquid nitrogen temperature to a strain of 2.1 (LNT-DPD Cu). Three distinct regions that are dominated by dislocation slip, shear banding and nanotwinning, form a multi-component nanostructure. The microstructure of each region has been quantified by transmission electron microscopy assisted by Kikuchi line analysis. Based on the structural parameters the stored energy of each region was evaluated, and the total energy can be assumed to be a linear additivity of that in each region weighted by the respective volume fraction. A microstructure based evaluation of the stored energy of multi-component nanostructure has been proposed.

Compressive fracture of Zr55Al10Ni5Cu30 bulk amorphous alloy at high temperatures

The fracture behavior of the Zr55Al10Ni5Cu30 bulk amorphous alloy under uniaxial compression at high temperatures has been investigated. At room temperature, the fracture occurred along the maximum shear plane which declined by 45degrees to the direction of the applied load, and a crack with serrated edge appeared on the ridge of the veins at the fracture surface for the Zr55Al10Ni5Cu30 bulk amorphous alloy. At high temperatures, the compressive fracture surface of the Zr55Al10Ni5Cu30 bulk amorphous alloy became much rougher than that at room temperature and steps appeared on the fracture surface. With increasing temperature, a different pattern from the vein-like morphology appeared on the fracture surface, which is very similar to the lava-flow. This type of fracture pattern is most likely due to the adiabatic heating created by plastic flow