Shear-band cavitation determines the shape of the stress-strain curve of 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.

Automated summary

Metallic glasses have a strong yield strength but exhibit unpredictable behavior after yielding, with large scatter in flow stress levels and strains at failure. X-ray tomography reveals that a strain-dependent internal evolution of shear-band cavities explains this postyielding response. The growth of cavities during plastic flow follows a power law and exhibits self-similar surface properties after fracture. These findings explain the large variability in plastic flow behavior and the coexistence of internal microcracking and shear-band plasticity in metallic glasses.