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Shear-band cavitation determines the shape of the stress-strain curve of metallic glasses
Summary
Researchers used X-ray tomography to reveal how shear-band cavitation governs the post-yield stress-strain behavior of metallic glasses, finding that macroscopic strain softening coincides with the first appearance of internal shear-band cavities and that cavity growth follows a power law with a fractal dimension consistent with self-similar fracture surface properties. These findings demonstrate that internal microcracking dynamics underlie the large variability in post-yielding flow stress and failure strain observed in metallic glasses.
Metallic glasses are known to have a remarkably robust yield strength, admitting Weibull moduli as high as for crystalline engineering alloys. However, their postyielding behavior is strongly varying, with large scatter in both flow stress levels and strains at failure. Using x-ray tomography, we reveal how a strain-dependent internal evolution of shear-band cavities underlies this unpredictable postyielding response. We demonstrate how macroscopic strain softening coincides with the first detection of internal shear-band cavitation. Cavity growth during plastic flow is found to follow a power law, which yields a fractal dimension and a roughness exponent in excellent agreement with self-similar surface properties obtained after fracture. These findings demonstrate how internal microcracking coexists with shear-band plasticity along the plastic part of a stress-strain curve, rationalizing the large variability of plastic flow behavior seen for metallic glasses.
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