Abstract
Mechanical properties of Fe-40Al alloys with C contents of 0.07 - 1.9 at.% were studied by uniaxial compressive creep and constant strain rate tests at temperatures from 600 °C to 750 °C. The dependence of both the creep resistance and the constant strain rate characteristics on the carbon content is not monotonous; the worst mechanical properties are observed in the alloys with 0.75 and 1.7 at.% C. The final heat treatment consisting in annealing at 1100 °C for 8 hours with quenching to oil has only a small influence on the creep rate. The stress and temperature dependence of the creep rate was determined by stepwise loading and evaluated in terms of the stress exponent n and the activation energy Q, respectively. These quantities can be interpreted by means of dislocation motion controlled by climb and by the presence of second phase particles. Deformation in the alloys with 0.75 and 1.7 at.% C occurs by the dislocation motion as in the single-phase FeAl matrix, eventually modified by the presence of dissolved carbon atoms (solid solution hardening). The dislocation motion is obstructed by tiny precipitates, probably of carbide κ, in the alloy with 0.07 at.% C and by particles of Al₄C₃ in the alloy with 1.9 at.%. Precipitates of carbide κ do not improve creep resistance efficiently at moderate carbon additions.

Key words
iron aluminides, creep, high temperature deformation

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