A criterion of the critical threshold of the maximum shear stress in bulk metallic glasses with cryogenic thermal cycling by statistics in nanoindentation

The shear transformation zones of metallic glasses have been widely studied by nanoindentation. In this work, the mathematic relationship between the relevant parameters is analyzed emphatically. Bulk metallic glasses were given different activation volumes by the cryogenic thermal cycling treatment. Nanoindentation experiments were carried out in a load-controlled loading mode. The critical threshold of the maximum shear stress, (Zmax)C, was obtained by the noise-reduction procedures and the statistical analysis. And the activation volume, V*, was obtained from the nonlinear slope by introducing a first-order polynomial. Based on the mean-filed theory, a criterion is successfully established, (Zmax)C = V*-& lambda;, where & lambda; = 0.30 & PLUSMN; 0.10. According to lots of previous studies on (Zmax)C and V* of metallic glasses, three applicable conditions of the criterion are extracted.

Automated summary

The shear transformation zones of metallic glasses were extensively studied using nanoindentation. The mathematical relationship between the relevant parameters was analyzed in detail. Cryogenic thermal cycling treatment was applied to the bulk metallic glasses to achieve different activation volumes. Nanoindentation experiments were conducted in a load-controlled loading mode. The critical threshold of the maximum shear stress, (Zmax)C, was determined through noise-reduction procedures and statistical analysis. The activation volume, V*, was obtained by introducing a first-order polynomial to analyze the nonlinear slope. Based on the mean-field theory, a criterion (Zmax)C = V* - λ was successfully established, where λ = 0.30±0.10. Three applicable conditions of the criterion were extracted from previous studies on (Zmax)C and V* of metallic glasses.