Evolution of microstructure of magnesium alloy AZ91D solidified with low-voltage electric current pulses

摘要

The microstructure evolution of magnesium alloy AZ91D solidified by a new solidification processing, low-voltage electric current pulse (LVECP), with different electric current pulses is investigated. The experimental results show that the dendrite growth is restrained and the microstructure is changed from larger dendrite grains to smaller nondendritic grains in the alloy by LVECP processing, and with certain current pulsing amplitude, the equiaxed, non-dendritic grains are gained in the alloy. Based on the experimental results, it is considered that the electric current pulses not only restrain the dendrite growth, but also enhance the nucleation rate. In addition, heat generation caused by LVECP will decrease the cooling rate of the melt and cause temperature fluctuation in the melt, which makes dendrite arms remelted and refined the grain of AZ91D alloy during the solidification.