Creep of face-centered-cubic {111} and {100} grains in FeCoNiCrMn and FeCoNiCrMn-Al alloys: Orientation and solid solution effects

摘要

In this study, creep behavior of the face-centered-cubic (FCC) {111} and (1001 grains in single-phase Fe20Co20Ni20Cr20Mn20 and dual-phase Fe(18)Co(18)Ni(20)Cr(18)Mn(18)A(18) high-entropy alloys (HEAs) was evaluated using a nanoindentation method over temperatures range of 300-600 degrees C. We measured the creep response of the two different grain orientations in the two alloys in order to study the orientation and solid-solution effects. Creep stress exponent (similar to 3.8-5.0) and activation energy (240-260 kJ/mol) were extracted and analyzed from stain rate-stress and stain rate-temperature data to provide information on the creep mechanism. The results indicated that creep was controlled by dislocation climb in both alloys at both orientations. However, we pointed out that, based upon activation energy value alone, it was difficult to identify which elemental constituent would be the dominant diffusing species responsible for vacancy diffusion during the climb. It was found that creep activation volume for the current two HEAs (140 angstrom(3) or similar to 12 Omega, where Omega is the atomic volume) at 600 degrees C is larger than that reported for the Ni-based superalloys (similar to 50-100 angstrom(3) or less) within a similar temperature range. The significance of this larger activation volume is also discussed.