Solidification behavior and crystal growth mechanism of aluminum under electric pulse

The solidification behavior and structure evolution of a directionally solidified pure aluminum were investigated, subjected to an electric pulse modification (EP, EPM). It was found that EPM led to an increase of the width of columnar grains, and that the growth of columnar grains was rendered more continuous. As illustrated by the cooling curves, the crystallization time of the pure aluminum increased, whereas the nucleation temperature was reduced by EPM. Judged by the X-ray diffraction (XRD) patterns, it was unraveled that EPM promoted the preference of low-index growth crystal planes, assisted by tuning pulsed voltages. An analysis of pole figures confirmed that some transitional high-index crystal planes have been also intermediated during the grain growth. As a consequence, three motifs were highlighted for EPM process, covering from the rotation around the same crystal zone axis, and around the same intersection point of crystal zone axis, to the stochastic high-index crystal plane rotation.