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High‐purity stoichiometric NiAl single crystals have been prepared by crucible‐free inductive zone melting under an Ar atmosphere. After a special annealing treatment at temperatures below 1200 K a residual resistivity ratio of better than 15 has been achieved. The crystals can be easily deformed in torsion already at room temperature. The dislocation mobility was investigated by internal‐friction measurements in the temperature range 300 to 1000 K. After torsional deformation at room temperature relaxation maxima were observed at about 550 and 800 K. Their relaxation strength depends on the crystal orientation and the amplitude of the torsional vibrations. Both maxima anneal already during the measurement and vanish after annealing at 1000 K. After an additional deformation in torsion at room temperature the maxima appear again. The results are discussed in terms of dislocation relaxations and dislocation pinning.

High-purity stoichiometric NiAl single crystals have been prepared by crucible-free inductive zone melting and afterwards well annealed at temperatures below 1200 K. Internal friction measurements of torsionally deformed single crystals show two relaxation maxima at 500 and 800 K which anneal during the measurement. The first maximum can be assigned to the dislocation motion by kinkpair formation and the annealing to pinning of these dislocations by interstitial impurity atoms. The second maximum is attributed to the Snoek-Köster relaxation of dislocations in the presence of mobile interstitial impurity atoms and the annealing to the pinning of dislocations by vacancies. The kink-pair formation enthalpy in NiAl was estimated.

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