Homogenization Behaviors of Low Frequency Electromagnetic Casting and Direct Chill Casting 7050 Aluminum Alloy

Abstract

7050 aluminum alloy ingots were produced by low frequency electromagnetic casting (LFEC) and direct chill casting (DC) respectively. As-cast microstructures and homogenization behaviors of LFEC and DC ingots were investigated experimentally. The optical microscope and DSC analyses shown that the grain size of LFEC ingot was finer and the content of constituents and eutectic structure was less than that of DC ingot. Accordingly, the homogenization behaviors of the LFEC and DC ingots were significantly different. The remnant constituents of LFEC ingot were less in content and smaller in size than that of DC ingot after homogenization at 480°C for various lengths of time. Similar to the dissolving of constituents, the LFEC ingot exhibited faster diffusion kinetics of alloying elements from grain boundary to inner. The concentrations of Cu, Mg and Zn inside grain of LFEC ingot after homogenization for 12 h were 2.4%, 2.2% and 6.5% respectively, but the DC ingots had not reach the level even for 48 h.