Abstract
We study the mechanical properties of nanoglass (NG) nanopillars with diameters from \unit[4.5]{nm} to \unit[54]{nm} by means of molecular dynamics simulations and compare the results with those obtained for nanopillars prepared from homogenous bulk glasses. Nanoglass nanopillars of two different types of glasses, namely Cu$_{64}$Zr$_{36}$ and Pd$_{80}$Si$_{20}$, were cut from samples prepared by nanoparticle consolidation. The influence of nanopillar diameter on the deformation behavior and strain localization is investigated. Moreover, cyclic loading is used to explore the origin of stress overshoots in the stress-strain curves of NGs. Finally, from the calculated properties a deformation map for NG and HG nanopillars is derived.
Highlights
Nanoglasses (NGs) are glassy materials with microstructural features on the nanoscale, which consist of glassy grains connected by glass–glass interfaces (Ivanisenko et al, 2018)
When reducing the sample size to the nanoscale, 15% plastic strain was observed in a 400 nm Sc75Fe25 NG nanopillar using in situ tensile tests in a transmission electron microscope (Wang et al, 2015)
The onset of strain softening occurs earlier in the large nanopillars: the stress of 36 and 54 nm NG nanopillars starts decreasing at an engineering strain of about 13–15%, in agreement with experimental results on a 400 nm Sc75Fe25 NG nanopillar showing about 15% plastic strain (Wang et al, 2015)
Summary
Nanoglasses (NGs) are glassy materials with microstructural features on the nanoscale, which consist of glassy grains connected by glass–glass interfaces (Ivanisenko et al, 2018) These interfaces are characterized by an excess volume (Jing et al, 1989; Sopu et al, 2009), a defective short-range order (SRO) (Ritter et al, 2011), and a different composition as compared with the glassy grains (Adjaoud and Albe, 2016; Wang et al, 2016a; Adjaoud and Albe, 2018). A systematic study of nanosized and microsized Sc75Fe25 HG and NG pillars by means of compression tests showed that both, yield strength and deformation mode, are size-dependent in HG pillars These properties, are size-independent in the NG pillars (Wang et al, 2016b), which was attributed to the microstructural features present in the NG. Molecular dynamic (MD) simulations revealed that glass–glass interfaces in NGs act as nucleation sites for shear transformation zones (STZs) and prevent strain localization, which leads to the more homogeneous deformation of NGs as compared with HGs (Sopu et al, 2011; Adibi et al, 2013; Albe et al, 2013; Adibi et al, 2014; Sopu and Albe, 2015; Adjaoud and Albe, 2019; Cheng and Trelewicz, 2019b)
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