日本金属学会誌

J. Japan Inst. Metals, Vol. 38, No. 10 (1974),
pp. 969-977

Internal Friction in Niobium Hydride

Muneyuki Amano1 and Yasuo Sasaki1

1National Research Institute for Metals, Tokyo

Abstract:

The internal friction in NbH0.43, NbH0.75 and NbH0.84 was measured in a temperature range from -170°C to 220°C. The observed internal friction was compared with the results of differential thermal analyses, electrical resistance measurements, electron diffraction and transmission electron microscopy.
Sharp damping peaks were observed at the temperature of the eutectoid transformation for NbH0.43 and the temperatures of the β - α' transformation for NbH0.75 and NbH0.84. Each alloy also showed a peak at the temperature of phase transformation associated with the change in ordering of hydrogen in the hydride phase.
A peak which is not associated with phase transformation was found below room temperature. This peak shifted to lower temperatures with increasing hydrogen content in the hydride phase. And, it showed a frequency dependence and its activation energy was about 30 kcal/mol. High background damping was observed in the temperature range from this peak to the temperature of the eutectoid or the β - α' transformation, and it showed a large amplitude dependence. Domain boundaries were frequently observed in the hydride phase and were very mobile under thermal stress caused by electron irradiation.
It is concluded that the peak which is not associated with the phase transformation is caused by a cooperative motion of hydrogen atoms at the domain boundaries in the hydride phase and the high background damping is attributed to the irreversible movements of the domain boundaries.


(Received 1974/05/14)

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