Electromagnetic Field Induced Structure Transition of Aluminum Alloys during Direct Chill Casting

Abstract

The structure transition induced by electromagnetic fields during the horizontal direct chill casting of 3004 aluminum alloy was investigated. Results show that the coarse columnar grains were transformed to medium-fine columnar and equiaxed grains with a transition region. Crystallographic analysis indicates that some arms were firstly detached from the coarse columnar dendrite and then formed fine grains with little change of orientation. With the increase of the electromagnetic fields, the grains growing from the later-detached arms exhibited a greater orientation deviation. When the electromagnetic fields approached the set value, more arms were detached and new grains showed totally random orientations. The structure transformation is related to the fragmentation of the dendrite arms by the forced convections.

Fig. 5 (a) All-Euler orientation micrograph corresponding to the microstructure in the dashed rectangular frame in Fig. 3(a), and (b) <100> pole figures corresponding to parts I–IV in (a), respectively.