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Title: Phase transformations, heat evolution, and atomic diffusion during slow heating of Al-rich Al/Zr multilayered foils

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 Al{sub 3}Zr 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 Al{sub 3}Zr 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.
Authors:
; ; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218-2689 (United States)
  2. Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616 (United States)
  3. (United States)
  4. High-Resolution Analytical Electron Microbeam Facility, Integrated Imaging Center, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
  5. Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
Publication Date:
OSTI Identifier:
22267778
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 24; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; AMORPHOUS STATE; CALORIMETERS; DIFFUSION; EVOLUTION; FOILS; FORMATION HEAT; HEAT; HEAT TREATMENTS; HEATING; LAYERS; PHASE TRANSFORMATIONS; THICKNESS