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Title: Grain Growth in Nanocrystalline Mg-Al Thin Films

We report that an improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing ~10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. In conclusion, the low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy and Environment Directorate
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental and Molecular Sciences Laboratory
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical & Computational Sciences Directorate
Publication Date:
Report Number(s):
PNNL-SA-113636
Journal ID: ISSN 1073-5623; PII: 4350; TRN: US1800443
Grant/Contract Number:
AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 48; Journal Issue: 12; Journal ID: ISSN 1073-5623
Publisher:
ASM International
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1413510

Kruska, Karen, Rohatgi, Aashish, Vemuri, Rama S., Kovarik, Libor, Moser, Trevor H., Evans, James E., and Browning, Nigel D.. Grain Growth in Nanocrystalline Mg-Al Thin Films. United States: N. p., Web. doi:10.1007/S11661-017-4350-0.
Kruska, Karen, Rohatgi, Aashish, Vemuri, Rama S., Kovarik, Libor, Moser, Trevor H., Evans, James E., & Browning, Nigel D.. Grain Growth in Nanocrystalline Mg-Al Thin Films. United States. doi:10.1007/S11661-017-4350-0.
Kruska, Karen, Rohatgi, Aashish, Vemuri, Rama S., Kovarik, Libor, Moser, Trevor H., Evans, James E., and Browning, Nigel D.. 2017. "Grain Growth in Nanocrystalline Mg-Al Thin Films". United States. doi:10.1007/S11661-017-4350-0. https://www.osti.gov/servlets/purl/1413510.
@article{osti_1413510,
title = {Grain Growth in Nanocrystalline Mg-Al Thin Films},
author = {Kruska, Karen and Rohatgi, Aashish and Vemuri, Rama S. and Kovarik, Libor and Moser, Trevor H. and Evans, James E. and Browning, Nigel D.},
abstractNote = {We report that an improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing ~10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. In conclusion, the low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.},
doi = {10.1007/S11661-017-4350-0},
journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
number = 12,
volume = 48,
place = {United States},
year = {2017},
month = {10}
}