A model revealing grain boundary arrangement-dominated fatigue cracking behavior in nanoscale metallic multilayers
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esearch Letter
A model revealing grain boundary arrangement-dominated fatigue cracking behavior in nanoscale metallic multilayers Fei Liang, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P. R. China; School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, P. R. China Dong Wang , Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano®, TU Ilmenau, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau, Germany Xi Li and Xue-Mei Luo, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P. R. China Peter Schaaf, Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano®, TU Ilmenau, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau, Germany Guang-Ping Zhang , Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P. R. China Address all correspondence to Guang-Ping Zhang at [email protected] (Received 2 May 2019; accepted 28 May 2019)
Abstract In order to reveal the quantitative relationship between fatigue crack deflection path and cross-sectional grain boundary (GB) arrangement of metallic nanolayered composites (NLCs), a stochastic model was established based on the interface-dominant fatigue damage for the ultrafinescale NLCs. The model indicates that the crack deflection length decreases with decreasing GB arrangement deviation and grain size of constituent layers. The observation and quantitative analysis of fatigue cracking behavior of the Cu/W multilayers with a layer thickness of 5 and 20 nm was conducted to verify the model.
Introduction Nanolayered composites (NLCs) have attracted much attention due to their excellent mechanical properties in recent years.[1–5] However, metallic NLCs always exhibit poor ductility due to the strongly constrained dislocation activities with decreasing individual layer thickness (h).[6,7] In recent years, some researchers mainly focused on the relationship between the length scale-dependent fracture mode of NLCs and the strengthening mechanism or the constraint effect of a ductile layer on a brittle layer.[8,9] When the multilayer thickness is decreased to a few nanometers and tens of nanometers, dislocation activity is considered to be strongly suppressed and fatigue cracks tend to be localized at weak layer interfaces[10–13] and grain boundaries (GBs) of constituent layers.[14–17] In recent years, the importance of tuning GB structure/morphology to enhance the extrinsic toughness of nanocrystalline materials is gradually revealed.[18–23] Through multiple crack deflection during fracture process, Daniel et al.[21] enhanced fracture toughness of nanocrystalline TiN films up to 150% by fabricating tilted columnar grains with chevron-like shape instead of the traditional columnar microstructure. However, the effect of GB
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