Solidified behavior and microstructure of high strength Al-Mg alloy under electromagnetic field simulated by direct current

Direct current was applied to Al-Mg alloy during solidification and the effect of current density on the microstructure was investigated. It was found that during solidification, the grain size first decreases and then increases. The length of columnar crystal near the positive electrode first increases and then decreases. When the current density is increased from 0 to 25 mA/mm(2), the grain size of alpha-Al decreases gradually and the length of columnar grain near the positive electrode increases. As the current density is greater than 25 mA/mm(2), the grain size of alpha-Al increases gradually and the length of columnar grain near the positive electrode decreases gradually. The change of columnar crystal length in the negative region is opposite to that in the positive region. The mechanical properties of the alloy under electromagnetic recombination were tested. The characteristics of grain refinement and growth are discussed from the perspectives of nucleation and growth, which reflects the common influence of Peltier effect and Joule effect on solidification structure.