Synergetic Effect of Sc Micro-alloying and Low-Frequency Electromagnetic Casting in 7A36 Aluminum Alloy with Enhanced Mechanical and Corrosion Properties

This study aims to investigate the combined effect of Sc micro-alloying and applying low-frequency electromagnetic casting (LFEC) on precipitation behavior, mechanical and corrosion properties of 7A36 aluminum alloy. The results indicate that when compared to the T6 state, the two-stage over-aging (T73) treatment causes the transformation of the grain interior eta ' phases into coarser eta ' and eta phases and leads to a more distinct appearance of precipitate free zone (PFZ). The addition of Sc results in the discontinuous and coarser formation of grain boundary precipitates (GBPs), and the Al3(Sc, Zr) phase particles contributes to the increased strength of 7A36 aluminum alloy. LFEC promotes the finer second phase and a finer distribution of grain interior precipitates, and dislocation movement bypasses a shorter distance and less energy is consumed, thus strength is decreased slightly. Meanwhile, the wider PFZ and the greater distribution spacing of the coarse GBPs contribute to a smaller intergranular fracture tendency, that's improve elongation of T6 and T73 alloys by 56.4% and 22.5% respectively, and contribute to improve corrosion resistance by blocking of intergranular corrosion channels. Based on the precipitation evolution, the synergy mechanism of Sc micro-alloying and LFEC processing is put forward in this paper.