The effect of small pre-strain on the internal friction and modulus of high-purity molybdenum I. The Occurrence of a large frequency ‘kink’ associated with β peaks

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Abstract
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 (10−5) curves taken in the same temperature range. We suggest that these peaks are β peaks arising from various interactions between dislocations and point defects. Since the modulus defect associated with a β peak can be ten times larger than that associated with a Debye relaxation and can be direct or inverse, the presence of β peaks can also account for the unusual frequency ‘kink’.