A comparative study has been made of the creep behaviour of stoichiometric Ni50Al50 and (Ni40Fe10)Al-50 over the temperature range 600-750 degrees C. It is confirmed that the addition of Fe improves the creep resistance of NiAl, decreasing appreciably its steady state creep rate. The rate controlling process is dislocation climb in Ni50Al50, which gives rise to a well developed subgrain substructure while dislocation glide appears to control the creep in (Ni40Fe10)Al-50. Almost, all the dislocations have Burgers vectors with b=(100), except for a few short segments with b=(110) found in the dislocation networks. In addition, numerous prismatic dislocation loops are observed in crept NiAl; they may be associated with a supersaturation of vacancies and the precipitation of impurity particles at intermediate temperatures. Lastly, it is found that the strengthening mechanisms are solid solution hardening as proved by transient compressive test results and the decrease of the diffusion coefficient by Fe additions according to the evidence provided in the literature. (c) 2006 Elsevier Ltd. All rights reserved.
- nickel aluminides
- dislocation geometry and arrangements
- based on NiAl
- electron microscopy