Internal friction caused by diffusion around a second-phase particle Al-Si alloy

The stress relaxation caused by diffusion round a second-phase particle has been measured by internal friction in Al-Si alloys. Reproducible clear internal-friction peaks were found at ∼420 K at a frequency of ∼ 1 Hz. These were unambiguously assigned to the presence of Si particles in Al. In accordance with a theory of the relaxation caused by diffusion along the matrix—particle interface, the relaxation time is proportional to the third power of the particle size. The activation energy and the pre-exponential factor of this diffusion are ∼ 0·92 eV and ∼ 3·9 × 10−5 m2/s, respectively. The magnitude of the relaxation strength agrees with the theory.