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Title: Grain Growth in Nanocrystalline Mg-Al Thin Films

Abstract

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.% 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 (150 °C), 473 K (200 °C) and 573K (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. The low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1422325
Report Number(s):
PNNL-SA-113636
Journal ID: ISSN 1073-5623; 49091; VT0505000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science; Journal Volume: 48; Journal Issue: 12
Country of Publication:
United States
Language:
English
Subject:
Electron microscopy; magnesium alloys; grain growth; precipitation; activation energy; grain growth exponent; N20602; Environmental Molecular Sciences Laboratory

Citation Formats

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., 2017. 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. Thu . "Grain Growth in Nanocrystalline Mg-Al Thin Films". United States. doi:10.1007/s11661-017-4350-0.
@article{osti_1422325,
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 = {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.% 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 (150 °C), 473 K (200 °C) and 573K (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. 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 = {Thu Oct 05 00:00:00 EDT 2017},
month = {Thu Oct 05 00:00:00 EDT 2017}
}