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

Abstract

In order to investigate the effects of Mn and Cu additions on solidification microstructure and high-temperature strength of cast AlFe alloys, we have fabricated various AlFe-based alloys with compositions of Al1%Fe, Al1%Fe1%Mn, Al1%Fe1%Cu, and Al1%Fe1%Cu1%Mn (mol%) solidified at different cooling rates (0.3 K·s11 and 145 K·s11). In the Al1%Fe binary alloy, the coarsened ª-Al13Fe4 phase with a needle-shaped morphology was often observed in the furnace-cooled sample (0.3 K·s11), whereas the cast sample (145 K·s11) exhibited several elongated ¡ phases surrounded by fine ¡/Al6Fe eutectic microstructure. Such a solidification microstructure was observed in the cast Al1%Fe1%Cu alloy, whereas the Al23CuFe4 phase was locally formed in the finally solidified zone in the furnace-cooled sample. In the Al1%Fe1%Mn alloy, the Al6(Fe, Mn) phase was formed regardless of the cooling rate. Finer ¡/Al6(Fe, Mn) two-phase eutectic microstructure was almost entirely occupied in the cast sample. The fine eutectic microstructure was observed in the cast Al1%Fe1%Cu1%Mn alloy as well. Compression tests for cast alloy specimens revealed that the Al1%Fe1%Cu1%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 AlFe alloys.