Measurement of the Zener relaxation in high-purity FeCr single crystals

In binary alloys the measurement of the so-called Zener relaxation may be u sed as a non-destructive method to determine the activation enthalpy of sel f diffusion. High-purity FeCr single crystals with a Cr content of 53 at % were prepared by containerless inductive zone melting under Ar atmosphere. The internal friction was measured between temperatures of 300 to 1200 K us ing an inverted torsion pendulum in the frequency range between 2 and SO Hz . A strong damping is observed below the Curie temperature of about 600 K d ue to domain wall motion. Above the ferromagnetic transition temperature a relaxation maximum occurs at about 920 K. The relaxation strength and the a ctivation parameters were determined for single crystals with (100), (110) and (111) orientation. The relaxation can be assigned to die stress-induced reorientation of short-range ordered Fe and Cr atoms, respectively. An ana lysis yielded an effective activation enthalpy of (2.95 +/- 0.3) eV showing no significant dependence on the crystal orientation. The orientation depe ndence of the relaxation strength and shear modulus indicates that jumps be tween nearest and next-nearest neighbor sites are involved. These results a re compared with results of self-diffusion measurements.