Strain Gradient in Micro‐Hardness Testing and Structural Relaxation in Metallic Glasses

An analytical model is proposed to quantitatively describe the depth‐dependence of Vickers micro‐hardness in metallic glasses. The approach is based on a shear bands distribution‐induced strain gradient during testing and was used to analyze thermal relaxation in the Zr₅₅Cu₂₀Al₁₀Ni₁₀Ti₅, Ni₅₃Nb₂₀Zr₈Ti₁₀Co₆Cu₃, and Mg₆₅Cu_12.5Ni_12.5MM₁₀ metallic glasses. It was shown that a decrease of the free volume leads systematically to a decrease of the alloy hardness. This analysis also gives an evaluation of the shear band thickness and the role of the elastic properties in the depth‐dependence of the Vickers micro‐hardness.