An experimental study of the Bordoni relaxation in aluminum

Bordoni relaxation (BR) of internal friction peaks in fcc metals was investigated experimentally using a pure aluminum crystal by a resonant bar method at 51 kHz. Each time after slight deformations or subsequent annealing, we measured the BR at temperatures between 78 K and 250 K. Usually the Bordoni relaxation consisted of two broad peaks, i.e., the Bordoni peak (B2 peak) at higher temperature (∼180 K) and Niblett-Wilks peak or shoulder (B1 peak) at lower temperature (∼120 K). It occurred unexpectedly that after an annealing at 800 K in air, four sharp internal friction peaks were found over the temperature range of the BR. The peak located at 120 K seems to be related with B1 peak. The remaining three peaks seem to be related with B2 peak.