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

Journal Article · Wed Jun 01 04:00:00 EDT 1977 · Acta Metall.; (United States)

DOI:https://doi.org/10.1016/0001-6160(77)90007-4· OSTI ID:7295279

Cowling, M J; Bacon, D J

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/sup 0/K. Specimens were tested in the as-annealed or 77/sup 0/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 less than or equal to 5 x 10/sup -5/, non-screw dislocation motion is controlled by double-kink nucleation on 71/sup 0/ segments, which is the ..cap alpha..' mechanism, and the motion of dislocations close to the screw orientation is controlled by kink migration, which is the ..cap alpha.. mechanism. Screw dislocation segments can move by double-kink nucleation at room temperature and this is the ..gamma.. mechanism. At higher amplitudes, dislocations moving by these mechanisms can overcome the barriers provided by interstitial impurity atoms.

• Research Organization: Liverpool Univ.
• OSTI ID: 7295279
• Journal Information: Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 25:6; ISSN AMETA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
DAMPING
DISLOCATIONS
ELEMENTS
FLOW STRESS
FRICTION
INTERNAL FRICTION
LINE DEFECTS
LOW TEMPERATURE
MECHANICAL PROPERTIES
MEDIUM TEMPERATURE
METALS
MONOCRYSTALS
REFRACTORY METALS
STRESSES
TANTALUM
TRANSITION ELEMENTS