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 degrees C. The alloys were tested in two different states: (i) cast and (ii) annealed at 1000 degrees 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 degrees C and with zirconium content of up to 2%. Creep resistance at temperatures of 700 and 900 degrees C increases with the increasing amounts of the secondary phases lambda(1) and tau(1). At the temperature of 650 degrees C, creep resistance is given not only by the volume fraction of particles but also by the ratio of tau(1)/lambda(1). This can be attributed to a more effective strengthening by particles of tau(1) resulting either from their mechanical properties or from their finer distribution. (C) 2013 Elsevier Ltd. All rights reserved.