THE EFFECT OF SMALL PRE-STRAIN ON THE INTERNAL-FRICTION AND MODULUS OF HIGH-PURITY MOLYBDENUM .1. THE OCCURRENCE OF A LARGE FREQUENCY KINK ASSOCIATED WITH BETA-PEAKS

The internal friction and frequency of high-purity molybdenum samples mounted as cantilevers vibrating at about 550 Hz have been measured between 80 and 530 K. The effect of small pre-strains was investigated. The main feature observed in one sample was a large frequency 'kink' between 350 and 450 K, which was most pronounced for pre-strains between 0. 13 and 0. 37%. Six damping peaks were identified in the high-strain-amplitude (10** minus **5) curves taken in the same temperature range. We suggest that these peaks are beta peaks arising from various interactions between dislocations and point defects. Since the modulus defect associated with a beta peak can be ten times larger than that associated with a Debye relaxation and can be direct or inverse, the presence of beta peaks can also account for the unusual frequency 'kink'.