Dislocation internal friction in high-purity and nitrogen-doped tantalum crystals

The dislocation internal-friction peaks between 10 and 3600K have been investigated in high-purity and in nitrogen-doped tantalum single crystals of different orientations following plastic deformation at 350 or 1980K. The experiments showed two damping peaks, one at 150, the other at 2500K (frequency f = 17 kHz), which are probably the α' and the α peak. The α' peak is observed particularly after low-temperature deformation. It is suggested that this peak is related to the thermally activated motions of geometrical kinks in screw dislocations. The α peak is thought to be due to the formation of double-kinks in non-screw (710) dislocations