Phase transformations, heat evolution, and atomic diffusion during slow heating of Al-rich Al/Zr multilayered foils
Abstract
We describe the energy and sequence of phase transformations in multilayered Al/Zr foils with atomic ratios of 3 Al:1 Zr during low temperature (<350 °C) heat treatments in a differential scanning calorimeter. The initial phase formed is an Al-rich amorphous phase that appears to grow by Zr diffusion through the amorphous phase. The subsequent nucleation and growth of tetragonal Al3Zr along the Al/amorphous layer interface is mediated by Al diffusion through the crystalline intermetallic phase. Diffusion coefficients associated with these processes are higher than expected from reports of diffusivities measured at higher temperatures. The inferred heat of formation of the tetragonal Al3Zr phase is 1240 ± 40 J/g (53 ± 2 kJ/mol atom). No anomalous variation in the energy or sequence of phase transformations is found with bilayer thickness for samples with bilayer thickness in the range of 17 nm to 90 nm despite anomalies in the bilayer dependence of self-propagating reaction velocities in the same foils.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 26, 2013
- Source ID
- 10.1063/1.4850915
Entities
People
- G. H. Campbell
- K. J. T. Livi
- Kaitlynn Fisher
- M. A. Bonds
- N. D. Browning
- R. Knepper
- S. C. Barron
- Timothy P. Weihs
Organizations
- Johns Hopkins University
- Lawrence Livermore National Laboratory
- Office of Naval Research