The effect of alternating magnetic field on the process of semi-continuous casting for AZ91 billets

Billets of AZ91 alloy under different alternating magnetic field conditions were examined. Effects of alternating magnetic field on microstructures, hardness, hot-tearing tendency and casting speed are studied. The results show that with a relatively low frequency of alternating magnetic field employed during the casting, the microstructures in the entire cross section of the billet are changed from columnar dendrites to equiaxed dendritic shapes; the hardness of billet is increased and the hot-tearing tendency is reduced. And it is possible to produce AZ91 billets at a relatively high casting speed with an alternating magnetic field.