Microstructures, mechanical properties and oxidation behaviour of single-phase Fe3Al (D0(3)) and two-phase alpha-Fe,Al (A2) + Fe3Al (D0(3)) Fe-Al-V alloys
Abstrakt
Microstructures, mechanical properties and oxidation behaviour of single-phase Fe3Al (D0(3)) and two-phase alpha-Fe,Al (A2) + Fe3Al (D0(3)) Fe-Al-V alloys have been studied. Alloying with vanadium substantially increases the strength of the single-phase alloys through solid solution hardening.
In addition, vanadium markedly increases the D0(3)/B2 transition temperature. The change from B2 to D0(3) at a given temperature yields an additional increase in strength.
The two-phase alloys have a fine-scaled coherent microstructure with D0(3) precipitates ranging between 10 and 30 nm in the as-cast state. However, marked coarsening of D0(3) is observed after annealing at 700 degrees C for 1000 h.
Up to this temperature the alloys show an appreciable flow stress and creep strength, comparable to those of other iron aluminide based alloys with coherent microstructures. Oxidation tests at 700-900 degrees C revealed formation of thick and porous Fe2O3 + Al2O3 scales above 700 degrees C.
Therefore, above 700 degrees C the oxidation behaviour of these alloys is inferior compared to that of other iron aluminide alloys with about the same Al content. This poor oxidation behaviour does not improve when 4-8 at.% Cr are added.