Effects of Mn and Cu Additions on Solidification Microstructure and High-Temperature Strength of Cast Al-Fe Binary Alloy

In order to investigate the effects of Mn and Cu additions on solidification microstructure and high-temperature strength of cast Al -Fe alloys, we have fabricated various Al -Fe-based alloys with compositions of Al-1%Fe, Al-1%Fe-1%Mn, Al-1%Fe-1%Cu, and Al-1%Fe- 1%Cu-1%Mn (mol%) solidified at different cooling rates (0.3 Kmiddots11 and 145 Kmiddots11). In the Al-1%Fe binary alloy, the coarsened 0-Al13Fe4 phase with a needle-shaped morphology was often observed in the furnace-cooled sample (0.3 Kmiddots11), whereas the cast sample (145 Kmiddots11) exhibited several elongated a phases surrounded by fine a/Al6Fe eutectic microstructure. Such a solidification microstructure was observed in the cast Al- 1%Fe-1%Cu alloy, whereas the Al23CuFe4 phase was locally formed in the finally solidified zone in the furnace-cooled sample. In the Al- 1%Fe-1%Mn alloy, the Al6(Fe, Mn) phase was formed regardless of the cooling rate. Finer a/Al6(Fe, Mn) two-phase eutectic microstructure was almost entirely occupied in the cast sample. The fine eutectic microstructure was observed in the cast Al-1%Fe-1%Cu-1%Mn alloy as well. Compression tests for cast alloy specimens revealed that the Al-1%Fe-1%Cu-1%Mn alloy exhibited the highest strength level among the studied alloy specimens, indicating the combined addition of Mn and Cu elements could be effective in improving the high-temperature strength of the cast Al -Fe alloys.