William Stratton Ph.D. Thesis - MINDS@UW Home

enabling us to make statements on how a different FEM results relate to changes in the sample
structure of high Al content amorphous alloys.
FEM on multiple high Al-content metallic amorphous alloys (Al92Sm8, Al88Y7Fe5, and
Al88Y7Fe4Cu1) found Al-like MRO present in the as quenched state of these materials.
Experiments on the deformation induced alloy Al92Sm8 found a different type of MRO, which
implies that the Al-like MRO in the as quenched material is associated with the devitrification
reaction of high Al-content amorphous alloys. Using our FEM theory, we determined that the
crystal Al-like volume fraction increases 60% when Al88Y7Fe5 is alloyed with Cu. This is
correlated with a measured increase in the crystal volume fraction in Al88Y7Fe5 and
Al88Y7Fe4Cu1 upon devitrification.
Taken together, this work supports the quenched-in nuclei hypothesis for high Al-content
amorphous alloy devitrification. In this picture, small proto-crystals are frozen into the material
during the rapid quench process and later act as nucleation sites for the high density of Al
nanocrystals that form upon devitrification. It is these proto-crystals that we measure with FEM.
This is a crystal growth mechanism rather than a grain coarsening mechanism. As seen by the
FEM results, these proto-crystals can be modified by alloying or processing to tailor the
macroscale properties of the material.
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