Dislocation damping in magnesium monocrystals
Hartman, David Eugene
Roberts, John M.
Master of Science
By employing a micro-strain gage, hysteresis loops were observed as a function of stress amplitude in magnesium single crystals from 83°K to 323°K, in the low frequency range (0.1 cps.). Broad relaxation peaks were found around 180°K. Activation energies associated with the peaks were about 0.33 ev., with a frequency factor of 108 cps. The stress amplitude dependence of the decrement was analyzed according to the Granato-Lucke and Teutonico-Granato-Lucke theories. The experimental results support the Teutonico-Granato-Lucke concept of pinned dislocations. A qualitative model is suggested to explain the symmetrical nature of the hysteresis loops, and the origin of the relaxation peak.