Effect of low frequency electromagnetic field on the constituents of a new super high strength aluminum alloy

Ingots of a new type of super high strength Al-Zn-Mg-Cu-Zr alloy have been produced by a process of low frequency electromagnetic casting (LFEC) and conventional direct chill (DC) casting, respectively. The effects of low frequency electromagnetic field on the constituents have been studied. The results show that the major constituents of this alloy at the grain boundary include the T(Al-Zn-Mg-Cu) phase, θ(CuAl2) and a eutectic structure, and no difference in the type of constituents between LFEC and DC ingots were observed. However, the effects of LFEC on the area fraction, distribution and size of constituents are very obvious. The LFEC process decreases the area fraction of constituents and eutectic structure at grain boundary in some degree (from about 8.6-9.86% to 7.4-8.15%), and reduces the grain boundary thickness very much (from about 0.83-0.98 μm to 0.383-0.528 μm). After homogenization treatment, the remnant constituents of the LFEC ingot are also less in content and smaller in size than that of DC ingots. Furthermore, both the as-cast and homogenization treated mechanical properties of ingot were improved by the process of LFEC.