Positron Annihilation Lifetime Studies of Deformed and Shock Loaded Tantalum
Abstract
Shock loading and quasi-static loading has been examined in annealed high purity tantalum. Investigation with positron annihilation lifetime spectroscopy, microhardness testing and optical microscopy shows increased dislocation density with increased true strain, but no significant increases with increased strain rate, aside from small degrees of dynamic recovery and twinning observed in shock loaded sample. The authors conclude that these results support the theory that deformation in tantalum is controlled by dislocation drag above the Peierls stress and that strain rate effects, which are dearly observed in most other materials, are suppressed. Quench hardening in annealed high purity tantalum has also been investigated. Microhardness testing results show quench hardening alter quenching from temperatures above 1100 deg C with cooling rates of approximately 200 deg C/min; these observations appear to be consistent with vacancy clustering. However, the temperatures required to produce quench hardening exceed the maximum estimates of temperatures achieved during shock loading. The authors conclude that quench hardening is not expected to have any significant effect on shock loading in tantalum.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 26, 1999
- Accession Number
- ADA365260
Entities
People
- David M. Stepp
- Phillip L. Jones
Organizations
- Duke University