Nanoquasicrystalline Al–Fe–Cr-based alloys. Part I: Phase transformations

Nanoquasicrystalline Al–Fe–Cr-based alloys composed of sub-micro-sized icosahedral quasicrystalline particles embedded in α-Al matrix have a higher strength at elevated temperature compared with commercial Al alloys. However, further improvement of the microstructural stability is desirable in order to maximize the elevated temperature strength. A detailed study of the effect on the microstructure and the phase transformations by the addition of Ti, V, Nb or Ta to a ternary Al93(Fe3Cr2)7 alloy was carried out using heat treatment and microstructural characterization. The addition of the fourth element leads to a refined microstructure and can stabilize the icosahedral topology, delaying the quasicrystalline icosahedral phase decomposition until a higher temperature is reached. The addition of Nb or Ta enabled a greater stabilization effect than the addition of Ti or V, retaining a microstructure similar to the as-spun state after heat treatment between 450 and 550 °C and even retaining icosahedral particles up to 550 °C. The outstanding microstructural stabilization obtained with addition of Nb or Ta leads to very promising applications in the automotive and aeronautic industries.