Effect of Intense Rolling and Folding on the Phase Stability of Amorphous Al-Y-Fe Alloys
A systematic examination of the effect of intense deformation on the crystallization behavior of amorphous Al85Y10Fe5, Al86Y9Fe5, and Al88Y5Fe7 alloys demonstrated a strong composition dependence of the crystallization reactions at true strain levels of about −500 pct. Primary crystallization occurs during the deformation of the Al88Y5Fe7 alloy, but for the Al86Y9Fe5 and Al85Y10Fe5 alloys, deformation-induced crystallization is not observed at a true strain of about −500 pct. At strain levels of the order of −1200 pct, the Al85Y10Fe5 alloy develops regions with primary Al, which is not observed during thermal processing of the same amorphous alloy without deformation. In addition, at strain levels of −1200 pct, a deformed Al88Y7Fe5 sample displays strong microstructural heterogeneities. Transmission electron microscopy (TEM) analysis showed the presence of nanocrystal dispersions adjacent to shear bands with a total width of about half a micrometer. The results demonstrate that the phase selection during deformation-induced crystallization can deviate from the thermally-induced phase selection. Novel phases and microstructures can thus be obtained from the deformation processing of amorphous alloys.
The authors gratefully acknowledge the helpful suggestions for the TEM analysis offered by Dr. Harald Rösner, Institute of Nanotechnology, Research Center Karlsruhe. The help of Thomas Jaster and John Lyons with the cold-rolling experiments is also acknowledged.
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