Microyielding in tantalum single crystals—II. High-amplitude damping

✍ Scribed by M.J Cowling; D.J Bacon

• Publisher: Elsevier Science
• Year: 1977
• Weight: 656 KB
• Volume: 25
• Category: Article
• ISSN: 0001-6160
• DOI: 10.1016/0001-6160(77)90007-4

✦ Synopsis

The damping at high amplitudes and low frequencies in tantalum single crystals of three purity levels has been determined from uniaxial compression tests at temperatures in the range 77-300 K. Specimens were tested in the as-annealed or 77 K-prestained states. The results have an amplitude-and temperature-dependence which can be related to previous studies of internal friction and to the microflow parameters of the same specimens. It is concluded that at total strain amplitudes s5 x IO-', non-screw dislocation motion is controlled by double-kink nucleation on 71' segments. which is the 2' mechanism. and the motion of dislocations close to the screw orientation is controlled by kink migration, which is the 1 mechanism. Screw dislocation segments can move by double-ink nucleation at room temperature and this is the 7 mechanism. At higher amplitudes. dislocations moving by these mechanisms can overcome the barriers provided by interstitial impurity atoms.