Hierarchical heterogeneity and an elastic microstructure observed in a metallic glass alloy

Heterogeneities in a Zr-based bulk metallic glass (BMG) were investigated using dynamic modulus mapping on a nanoindentation platform, revealing a complex elastic microstructure consisting of interpenetrating locally stiff and compliant regions with characteristic feature lengths on the order of 100 nm. The unique microstructures were observed in as-cast, annealed and laser-processed materials. Surprisingly, at various mapping locations across the cast sample cross sections, the elastic microstructures displayed directional alignment of the features with the mold surface. The results introduce an unprecedented spatial regime of elastic variations in monolithic BMGs that may contribute towards a more complete understanding of structure-property relationships in these materials, especially with regards to global deformation behavior.

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