Upward modulus trend in NiAl and NiFeAl single crystals

Dynamic Young modulus, torsion modulus and elastic energy dissipation were measured in Ni(56.2)Fe(0.3)Al(43.1)Ta(0.)3Mo(0.1) (NiAl crystal) and Ni56.6 Fe12.3Al30.2Hf0.6(Al2O3)(0.3) (NiFeAl crystal). The elastic constant C' = ( C-11 - C-12)/2 has in both alloys a positive temperature derivative: (dC'/d T)>0 from 150 K up to 1300 K. The elastic energy dissipation exhibits a Deb ye-like peak whose activation energy is 2.36+/-0.05 eV in NiAl and 1.98+/-0 .09 eV in NiFeAl. The peak is described as a Zener's pair reorientation. (C ) 2000 Elsevier Science S.A. All rights reserved.