An experimental instrument for solidification and in situ characterization of the nucleation behavior of high-melting metal under a high magnetic field.

ABSTRACT

A specially designed experimental apparatus suitable for commercial superconductor magnet is used for solidification and in situ characterization of the nucleation behavior of high-melting metals. In order to carry out solidification experiments under a high magnetic field (HMF), the sample cell in the experimental device has two stations for repeated verification experiments of two same samples or comparative experiments of two different samples. Meanwhile, a metal specimen and a reference (α-Al2O3) are placed in the sample cell to characterize the nucleation behavior in situ. Using this experimental device, the nucleation behaviors of Al-7wt. %Si alloy and pure Cu under a HMF were investigated. The results show that the undercoolings of Al-7wt. %Si alloy and pure Cu increase under the HMF. Furthermore, the applied HMF decreases the activation energy of Al-7wt. %Si alloy and increases the nucleation work. Based on the magnetohydrodynamic effect, the change in undercooling and nucleation work could be partly attributed to the restrained thermal convection by the HMF in this study.