Abstract
This paper describes the structure and properties of cast Fe3Al-based alloy doped with 15 at. % of silicon and 2 at. % of molybdenum. The higher content of silicon is useful for the enhancement of high-temperature mechanical properties or corrosion resistance of iron aluminides but deteriorates their workability due to increased brittleness. It was found that the presence of both alloying elements leads to an increase of values of the high-temperature yield stress in compression. The heat treatment (annealing at 800 °C for 100 h) used for the achievement of phase stability causes the grain coarsening, so the values of the high-temperature yield stress in compression are lower at 600 °C and 700 °C in comparison to values measured for the as-cast state. This stabilization annealing significantly improves the workability/machinability of alloy. Furthermore, the higher silicon content positively affects the values of the thermal expansion coefficient that was found to be lower in the temperature range up to 600 °C compared to alloys with lower content of silicon.
Highlights
The Fe3 Al-based iron aluminides are considered a suitable material for high-temperature application [1,2,3]
The fine dispersion can be formed by both types of secondary phase particles because the secondary phase particle formation can be influenced by molybdenum in two possible ways: (a) molybdenum participates in phase formation directly, so the phase Fe–Mo–Si forms; (b) molybdenum only supports the formation of Fe3 Si phase, analogically to Si-supported formation of Al4 C3 phase in the case of Fe–Al-based iron aluminides [23]
Silicon addition in the higher amount (15 at. %) causes the significant increase of values of the high-temperature yield stress in compression of Fe-28Al-15Si-2Mo alloy in the as-cast state compared to alloys with 5 at. % of silicon [1], primarily due to a higher level of solid strengthening solution
Summary
The Fe3 Al-based iron aluminides are considered a suitable material for high-temperature application [1,2,3]. They have many benefits, such as low weight and excellent corrosion resistance, as well as resistance to an aggressive environment. The poor ductility and workability of cast binary alloys at room temperature were an obstacle to wider use. The ductility at room temperature of the ordered Fe3 Al and Fe–Al phases varies with the degree of ordering, with a relative maximum ductility of about 8% at about. Most of the mechanical or physical properties of iron aluminides are sensitive, among other things, to the presence of alloying elements, and can be improved by using them [4,5]
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