Unusually thick shear-softening surface of micrometer-size metallic glasses
Jingyan Dong, Y. Huan, B. Huang, Jun Yi, Y.H. Liu, Baoan Sun, Wei Wang, H. Y. Bai
Abstract
upon glass transition, yet it still behaves solid-like. Strikingly, the surface thickness estimated from the shear-modulus softening is at least 400 nm, which is approximately one order of magnitude larger than that revealed from the glass dynamics. The unusually thick surface is also confirmed by measurements using X-ray nano-computed tomography, and this may account for the brittle-to-ductile transition of the MGs with size reductions. The unique and unusual properties at the surface of the micrometer-size MGs are physically related to the negative pressure effect during the thermoplastic formation process, which can dramatically reduce the density of the proximate surface region in the supercooled liquid state.