Microstructure and High-Temperature Strength of Fe-Al-Si(-Mo) Alloys with Refractory Metal Additives

The iron aluminides are intended as materials for high-temperature applications. The effect of Fe 3 Al-type iron aluminide multi-alloying with silicon, molybdenum, and vanadium/tungsten on the high-temperature strength was studied. The contribution of the different strengthening mechanisms to overall strengthening during high-temperature deformation in compression was discussed. It has been shown that the addition of vanadium or tungsten significantly increases the yield stress values, especially in the temperature range of 700–800°C. The influence of heat treatment on the structure and yield stress values was also investigated. After long-term annealing at 800°C, a slight decline in yield stress values occurs for both alloys compared to the as-cast state due to the precipitation of secondary phase particles. In the case of the Fe28Al5Si2Mo1W alloy, this yield stress decrease is partly compensated by the strengthening caused by fine incoherent precipitates. After short-term annealing at 1200°C, the yield stress reaches the highest values in the entire temperature range for both alloys, Fe28Al5Si2Mo1W and Fe28Al5Si2Mo1V, due to the presumed presence of new phase nuclei verified by prolongation of annealing time.