Eleventh International Conference on Internal Friction and Ultrasonic Attenuation in Solids
J. Phys. IV France 06 (1996) C8-345-C8-348
Anelastic Relaxations in Aluminium with Ultrafine Grain StructureE. Bonetti1, L. Pasquini1, E. Sampaolesi1 and M. Alvisi2
1 Dipartimento di Fisica, Università di Bologna and Istituto Nazionale per la Fisica della Materia, Viale Berti Pichat 6/2, 40127 Bologna, Italy
2 Istituto Nazionale per la Fisica della Materia, Dipartimento di Scienza dei Materiali, Via Arnesano, 73100 Lecce, Italy
The elastic energy dissipation coefficient and dynamic elasticity modulus were measured in the 3-4000 Hz frequency range by an inverted torsion pendulum and a vibrating reed technique on nanocrystalline aluminium samples obtained by mechanical attrition. The anelasticity spectra in the 300-700 K range on as-prepared samples with average grain size in the 20-40 nm range strongly depends on low temperature annealing treatments. A relaxational damping peak P1 at 460 K (3Hz) is observed in samples after thermal annealing without appreciable grain growth. A second peak P2 located at higher temperatures occurs when the grain size exceeds 100 nm.
© EDP Sciences 1996