Mechanical Characterization of Bulk Metallic Glass

The Challenge

Bulk metallic glasses offer exceptional mechanical resistance that makes them attractive substitutes for conventional crystalline metals in precision and micromechanical applications. However, predicting their durability in real systems remains difficult. Hardness alone, the traditional indicator of wear and scratch resistance, is too imprecise for these amorphous materials. Additional parameters reflecting the structural state must be considered to accurately predict the robustness of metallic glasses in service.

The Solution

This research conducted indentation and scratch tests on Cu47Zr46Al7 bulk metallic glass using the bonded interface technique to reveal subsurface deformation mechanisms. The study analyzed shear banding activity below and along scratch grooves to understand how the specific plastic deformation mechanisms of metallic glasses affect scratch resistance.

Impulse excitation testing provided the baseline elastic modulus measurements essential for characterizing the mechanical state of cast BMG samples. The correlation between elastic properties and scratch behavior helps establish the relationship between fundamental material parameters and practical wear resistance.

Key takeaway: Shear band length on the surface correlates with subsurface shear band length and scratch resistance, offering a practical surface indicator that eliminates the need for the bonded interface technique.

Results

The research discovered that shear band length below the scratch groove correlates with both scratch resistance and the length of surface-visible shear bands. This provides a practical surface indicator for evaluating scratch resistance without requiring the challenging bonded interface technique. The findings advance understanding of how strain softening affects metallic glass durability, enabling better prediction of performance in mechanical and tribological applications.