Nanocrystal formation in gas-atomized amorphous Al85Ni10La5 alloy |
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Authors: | Zhihui Zhang Nancy Yang Yizhang Zhou Enrique J. Lavernia |
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Affiliation: | 1. Department of Chemical Engineering and Materials Science , University of California , Davis, CA 95616, USA zhizhang@ucdavis.edu;3. Sandia National Laboratories , CA 94550, Livermore, USA;4. Department of Chemical Engineering and Materials Science , University of California , Davis, CA 95616, USA |
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Abstract: | An Al85Ni10La5 amorphous alloy, produced via gas atomization, was selected to study the mechanisms of nanocrystallization induced by thermal exposure. High resolution transmission electron microscopy results indicated the presence of quenched-in Al nuclei in the amorphous matrix of the atomized powder. However, a eutectic-like reaction, which involved the formation of the Al, Al11La3, and Al3Ni phases, was recorded in the first crystallization event (263°C) during differential scanning calorimetry continuous heating. Isothermal annealing experiments conducted below 263°C revealed that the formation of single fcc-Al phase occurred at 235°C. At higher temperatures, growth of the Al crystals occurred with formation of intermetallic phases, leading to a eutectic-like transformation behaviour at 263°C. During the first crystallization stage, nanocrystals were developed in the size range of 5 ~ 30 nm. During the second crystallization event (283°C), a bimodal size distribution of nanocrystals was formed with the smaller size in the range of around 10 ~ 30 nm and the larger size around 100 nm. The influence of pre-existing quenched-in Al nuclei on the microstructural evolution in the amorphous Al85Ni10La5 alloy is discussed and the effect of the microstructural evolution on the hardening behaviour is described in detail. |
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Keywords: | amorphous alloys crystallization eutectic Al-Ni-La alloy |
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