Effect of low frequency electromagnetic field on casting crack during DC casting superhigh strength aluminum alloy ingots

Abstract

Super high strength aluminum alloys are very important materials to the aerospace industries, however, cracks often occur during the DC casting process because of their high alloying element content. In this paper, a new low frequency electromagnetic casting (LFEC) process is used to study the possibility of eliminating casting cracks. The results show that a low frequency electromagnetic field eliminates cracks effectively. Under a low frequency electromagnetic field, temperature gradients in the mould are smaller, elements distributions are more uniform, sump depth is lower, and the grains are finer and have a more uniform spherical shape, so the internal stress in ingots is lower than that of ingots processed by conventional DC casting. The LFEC decreases the grain size, constituent size, and area fraction of grain boundary eutectics, which is helpful for thinning the liquid film between grains and improving high-temperature plasticity and strength. These factors improve the cracking resistance of the alloy. Decreasing internal stress and increasing cracking resistance eliminate cracks in DC cast ingots.