Influence of silicon content on phase development in Al-Fe-V-Si alloys

Al-Fe-V-Si alloys are promising materials for aviation and aerospace industries due to their high strength, good thermal stability and low weight. The influence of Si concentration on the mechanism of microstructure development and phase constitution in Al-Fe-V-Si alloys is studied in this work. A new mechanism of microstructure development during annealing of these alloys is proposed. The phase formation in alloys containing more than 3 wt.% Si could be associated with two successive processes. The decomposition of supersaturated Al matrix starting at 450 K is associated with the growth of secondary Si-phase. The second stage is observed above 600 K where growth of α13 quaternary intermetallics is experimentally proved. The experimental data directly and indirectly support the hypothesis that in this case the formation of a secondary silicon phase is a key factor for additional formation of fine α13 quaternary intermetallics by their easier nucleation on silicon substrate.