Effects of Mn and Cu Additions on Solidification Microstructure and High-Temperature Strength of Cast Al–Fe Binary Alloy
Naoki Okano, Naoki Takata, Asuka Suzuki, Makoto Kobashi
Abstract
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 K·s−1 and 145 K·s−1). In the Al–1%Fe binary alloy, the coarsened θ-Al13Fe4 phase with a needle-shaped morphology was often observed in the furnace-cooled sample (0.3 K·s−1), whereas the cast sample (145 K·s−1) exhibited several elongated α phases surrounded by fine α/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 α/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.