Nanosecond Time Resolved Electron Diffraction Studies of the (Alpha) to (Beta) Transition in Pure Ti Thin Films using the Dynamic Transmission Electron Microscope (DTEM)
The transient events of the {alpha}-{beta} martensitic transformation in nanocrystalline Ti films were explored via single shot electron diffraction patterns with 1.5 ns temporal resolution. The diffraction patterns were acquired with a newly constructed dynamic transmission electron microscope (DTEM), which combines nanosecond pulsed laser systems and pump-probe techniques with a conventional TEM. With the DTEM, the transient events of fundamental material processes, that are far too fast to be studied by conventional bulk techniques, can be captured in the form of electron diffraction patterns or images with nanosecond temporal resolution. The transient phenomena of the martensitic transformations in nanocrystalline Ti is ideally suited for study in the DTEM, with their rapid nucleation, characteristic interface velocities {approx}1 km/s, and significant irreversible microstructural changes. Free-standing 40-nm-thick Ti films were laser-heated at a rate of {approx}10{sup 10} K/s to a temperature above the 1155 K transition point, then probed at various time intervals with a 1.5-ns-long, intense electron pulse. Diffraction patterns show an almost complete transition to the {beta} phase within 500 ns. Postmortem analysis (after the sample is allowed to cool) shows a reversion to the {alpha} phase coupled with substantial grain growth, lath formation, and texture modification. The cooled material also shows a complete lack of apparent dislocations, suggesting the possible importance of a ''massive'' short-range diffusion transformation mechanism.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 883565
- Report Number(s):
- UCRL-CONF-217740; TRN: US200615%%135
- Resource Relation:
- Conference: Presented at: Frontiers of Electron Microscopy in Materials Science, Kastel Vaalsbroek, Netherlands, Sep 25 - Sep 30, 2005
- Country of Publication:
- United States
- Language:
- English
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