Unusual internal friction and its size dependence in nanoscale metallic glasses

GJ Yang and RS Wang and MX Wang and LF Liu and LT Kong and JF Li, JOURNAL OF APPLIED PHYSICS, 128, 055103 (2020).

DOI: 10.1063/5.0013705

The internal friction of Cu50Zr50 metallic glass nano-pillars was investigated by using molecular dynamics simulations. An unusual non- monotonic variation of internal friction is revealed against the size of the specimen, which differs significantly from that of the bulk metallic glass. Meanwhile, by analyzing the rearranged atoms with high mobility, which play a vital role in affecting the internal friction, it is found that the rearrangement of surface atoms is more significant than that of the bulk ones, and their fraction depends on the sample size as well. With reducing the sample size, the fraction of rearranged atoms in the surface region increases, which could be described by an exponential equation. This finding suggests that the size dependence of internal friction originates directly from the different fractions of the rearranged atoms in the surface region of nano-pillars. Furthermore, a phenomenological model was established to describe the internal friction of the nano-pillars against their diameters. The presented results provide a quantitative insight into the size effect on internal friction in nanoscale metallic glasses, also shedding light on the atomistic mechanism of surface relaxation of amorphous solids.

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