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Variation of hardness and modulus across the thickness of Zr-Cu-Al metallic glass ribbons

2013-01-01
Melgarejo, Z. Humberto
Jakes, J.E.
Hwang, J.
Kalay, Yunus Eren
Kramer, M.J.
Voyles, P.M.
Stone, D.S.
We investigate through-thickness hardness and modulus of Zr50Cu45Al5 metallic glass melt-spun ribbon. Because of their thinness, the ribbons are challenging to measure, so we employ a novel nanoindentation based-method to remove artifacts caused by ribbon flexing and edge effects. Hardness and modulus vary approximately linearly across the thickness but, unlike bulk ingots, the side of the ribbon that cooled most quickly had the highest hardness and modulus. This “inverse” variation may be caused by the fast-moving solidification front, which might conceivably, for instance, push free volume in advance of it. Annealing near T g causes both hardness and modulus to increase and become more uniform across the thickness.