In situ SEM indentation of a Zr-based bulk metallic glass at elevated temperatures

The elevated temperature indentation response of a Zr-based bulk metallic glass (BMG) was examined using a novel in situ SEM indentation system modified with tip and sample heating. Hardness was found to linearly increase with temperature from 7 GPa at 25 °C to 7.6 GPa at 200 °C, while the modulus remained constant within measurement accuracy. Adhesion between indenter and the BMG was observed to increase with increasing temperature. Both the number and pointed morphology of the surface shear offset displacements were found to decrease with increasing temperature. Conversely, the magnitude of the load drops/serrations in the load displacement curve was found to increase dramatically with temperature. The transitions from smooth to serrated flow were observed to fall within the temperature–strain rate ranges observed by other researchers in uniaxial compression.

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► First in situ mechanical property measurement on BMGs at elevated temperature.
► Low drift due to indenter and sample heating allowed quantitative measurements.
► Shear banding increases in magnitude and sub-surface localisation with temperature.
► Smooth to serrated flow transition mapped with strain rate and temperature.