Tian Xue-lei

Short-Range and Medium-Range Order in Liquid Cu-Ni Alloy

The liquid structure of the Cu70Ni30 alloy has been investigated using a θ-θ high-temperature x-ray diffractometer. At all temperatures above its liquidus, a distinct pre-peak has been found around a scattering vector magnitude of 13.5nm-1. The height of the pre-peak decreases gradually with increasing temperature but it clearly exists up to a temperature of 1400°C. This behaviour indicates that stable medium-range order atomic clusters exist in the melt. It is concluded that the short-range order atomic clusters of the liquid Cu70Ni30 alloy mainly consist of Cu atoms with centred Ni atoms. The appearance of the pre-peak in the structure factor of the liquid Cu70Ni30 alloy is caused by the interaction between centred Ni atoms locating in the neighbouring atomic clusters.

Viscosity measurements of Fe-Si-B-Cu-Nb-C metallic glass melts by an oscillating crucible method

Dependence of the dynamic viscosity of new type of Fe-based amorphous alloy (Fe68.5Si13.5B9Cu1Nb3C5) melt on temperature is investigated by using a torsional oscillation viscometer. The temperature dependence of the viscosity can be fitted by the Arrhenius relation and Fulcher expression as ln η = 0.082 + 1463.48/T and ln η = 6.75×10-5 + 954.71/(T-608.36), where η is the viscosity in units of cP and T is the temperature in units of K. The results show that the Arrhenius relation is more suitable in high temperature region, while the Fulcher expression is more appropriate in undercooled region. Combining the Differential scanning calorimetry data and free-volume model, the glass forming ability of Fe68.5Si13.5B9Cu1Nb3C5 alloy is discussed.

Effects of nickel on the crystallization of Zr70Cu20Ni10 amorphous alloy

Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) are employed to investigate the effects of nickel on the crystallization of the amorphous Zr70Cu20Ni10 alloy. We have found that the crystallization process of the amorphous Zr70Cu20Ni10 alloy is strongly influenced by the addition of nickel. Addition of 10 at% Ni to the Zr70Cu30 amorphous alloy makes the crystallization process proceed from a single-stage mode to a double-stage mode. The activation energy for crystallization of the amorphous Zr70Cu20Ni10 alloy is calculated to be about 388kJmol-1 on the basis of the Kissinger equation. The effects of nickel on the crystallization of the amorphous Zr70Cu20Ni10 alloy are discussed in terms of the genetics of metals.