Continuous and discontinuous grain coarsening in a fine-grained particle-containing Al-Sc alloy
- School of Materials Science and Engineering, University of New South Wales, UNSW, Sydney, NSW 2052 (Australia)
- School of Materials, University of Manchester, Grosvenor St, Manchester M17HS (United Kingdom)
An Al-0.2 wt% Sc alloy was solution treated, deformed by equal channel angular pressing (ECAP) to an effective true strain of 9.2 then aged for 3 h at 350 deg C to produce a fine-grained (0.8 {mu}m diameter) microstructure containing a large fraction ({approx}0.7) of high angle grain boundaries (HAGBs). This ageing treatment also generated a relatively uniform dispersion of 5 nm diameter Al{sub 3}Sc particles. Grain stability was investigated at temperatures up to 550 deg C using SEM, EBSD and TEM. It was found that the fine-grain structure was remarkably stable at temperatures up to 500 deg C with grain coarsening occurring gradually with no marked change in the grain size distribution, texture and grain boundary character. This homogeneous coarsening behaviour is usually termed continuous recrystallization. In this regime, both the fine-grained microstructure and Al{sub 3}Sc particles exhibit third order coarsening kinetics with dR/dt {proportional_to} dr/dt which indicates that grain coarsening is controlled by the rate of particle growth with the latter controlled by bulk diffusion of scandium in the Al matrix. During extended annealing at 500 deg C and for short times at higher temperatures, there is a notable transition from continuous to discontinuous grain coarsening whereby a small number of grains grow rapidly to produce a coarse (>10 {mu}m) grain size. An analytical mean field model of grain coarsening in particle-containing alloys was shown to adequately predict this transition in coarsening behaviour.
- OSTI ID:
- 20637155
- Journal Information:
- Acta Materialia, Vol. 53, Issue 4; Other Information: DOI: 10.1016/j.actamat.2004.11.006; PII: S1359-6454(04)00678-0; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 1359-6454
- Country of Publication:
- United States
- Language:
- English
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