The microstructure change in the Vickers indent of the Zr65Al7.5Ni10Cu12.5Ag5 metallic glass at room temperature is investigated by transmission electron microscopy. It is found that the indentation-induced crystallization occurs namely underneath the indenter edges, where viscous flow is involved and crystals with the size larger than 1 μm appeav. The selected area electron diffraction shows that the crystalline phases are stable tetragonal CuZr2 or NiZr2, but not the icosahedral one that grows as metastable phase on heating. The local temperature rise during indentation can be ignored, which further suggests that the mechanically induced crystallization in a metallic glass is attributed to the viscous flow rather than the local heating effect.
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