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 η′ phases into coarser η′ and η 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.

Graphic Abstract