On the shear resistance and strain-softening sensitivity in the scratch response of a Cu47Zr46Al7 bulk metallic glass

The high mechanical resistance of metallic glasses makes them innovative substitutes for conventional crystalline metals in mechanical and micromechanical applications, but their durability in real system remains difficult to evaluate. Historically, the hardness has been regarded as the most crucial parameter in predicting the wear and the scratch resistance of materials. Metallic glasses are no exception to this convenient but too imprecise rule. It is now generally admitted that additional mechanical parameters, reflecting the structural state, must be taken into account to predict more accurately the robustness of metallic glasses. Using the bonded interface technic, indentation and scratch tests were conducted on a Cu 47 Zr 46 Al 7 (at.%) metallic glass to evaluate the role of the specific plastic deformation mechanisms of metallic glasses during the formation of a scratch groove. The analysis of shear banding activity below and along the scratch helps to explain the observed morphology of the shear bands and the consequence of associated strain softening on the scratch depth is highlighted. The length of the shear bands below the scratch groove is found to be correlated with the scratch resistance as well as with the length of the shear bands observed on the surface. This offers a useful surface indicator to evaluate scratch resistance without the use of the challenging bonded interface technique for future studies