The effect of Zr addition on creep of Fe-30 at.% Al alloys

Compressive creep of alloys based on Fe-30 at.% Al with zirconium additions in the range of 0.4–5.2 at.% was studied at temperatures from 650 to 900 °C. The alloys were tested in two different states: (i) cast and (ii) annealed at 1000 °C for 50 h. Stress exponents and activation energies were estimated. The values of the stress exponent n can be explained by dislocation motion controlled by climb and by the presence of second-phase particles. Higher stress exponents were detected only at the temperature of 900 °C and with zirconium content of up to 2%. Creep resistance at temperatures of 700 and 900 °C increases with the increasing amounts of the secondary phases λ1 and τ1. At the temperature of 650 °C, creep resistance is given not only by the volume fraction of particles but also by the ratio of τ1/λ1. This can be attributed to a more effective strengthening by particles of τ1 resulting either from their mechanical properties or from their finer distribution.