Publications
Nanocrystal formation in gas-atomized amorphous Al85Ni10La5 alloy
An Al{sub 85}Ni{sub 10}La{sub 5} 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, Al{sub 11}La{sub 3}, and Al{sub 3}Ni 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 behavior 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 Al{sub 85}Ni{sub 10}La{sub 5} alloy is discussed and the effect of the microstructural evolution on the hardening behavior is described in detail.