Shock-induced phase transformation in tantalum
1Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, PO Box 808, L-352, Livermore, CA 94551-9900, USA. hsiungl@llnl.gov
Summary
Pure tantalum and tantalum-tungsten alloys were studied under high pressure. A shock-induced omega phase transformation was observed in Ta-10W due to suppressed dislocation recovery, unlike pure Ta and Ta-5W.
Area of Science:
- Materials Science
- Metallurgy
- Shock Physics
Background:
- Tantalum (Ta) and its alloys are critical in high-pressure applications.
- Understanding phase transformations under extreme conditions is vital for material design.
- Dislocation structures significantly influence material behavior under shock loading.
Purpose of the Study:
- To investigate the effects of explosive shock loading on pure tantalum and tantalum-tungsten alloys.
- To identify the conditions leading to shock-induced phase transformations.
- To elucidate the role of dislocations in phase transitions.
Main Methods:
- Transmission Electron Microscopy (TEM) was employed to analyze microstructures.
- Pure Ta, Ta-5W, and Ta-10W alloys were subjected to explosive shock at 30 GPa.
- Microstructural analysis focused on dislocation density and phase identification.
Main Results:
- Pure Ta and Ta-5W exhibited cellular dislocation structures without an omega phase.
- Ta-10W showed a shock-induced omega (hexagonal) phase transformation.
- The transformation in Ta-10W correlated with suppressed dynamic recovery of dislocations at densities > 1 × 10^12 cm^-2.
Conclusions:
- Shock-induced omega phase formation is dependent on alloy composition and dislocation dynamics.
- Suppressed dynamic recovery of dislocations is a key factor for the [Formula: see text] transition in Ta-10W.
- A dislocation-based mechanism is proposed for the observed shock-induced phase transformation.
