Molecular dynamics simulations of nanoindentation and scratch in Cu grain boundaries

• Shih-Wei Liang,
• Ren-Zheng Qiu and
• Te-Hua Fang

Beilstein J. Nanotechnol. 2017, 8, 2283–2295, doi:10.3762/bjnano.8.228

• . Since the atoms behind the grain boundary were destroyed by the scratch, the slip and the pile up increased gradually. The accumulation of atoms was more obvious at higher processing distances. The destruction of the grain boundary restricted the resistance of the force transmission. Moreover, shear

• bands were found under the zone of accumulation of atoms. As shown by the slip vector diagrams of the vertical grain boundary with a 20° angle (Figure 13b), the slip was found to be concentrated on the left side of the grain boundary for the 5 nm scratch. No clear dislocation through the grain boundary

A new approach to grain boundary engineering for nanocrystalline materials

• Shigeaki Kobayashi,
• Sadahiro Tsurekawa and
• Tadao Watanabe

Beilstein J. Nanotechnol. 2016, 7, 1829–1849, doi:10.3762/bjnano.7.176

• high-cycle fatigue may result from a rapid migration of low-angle boundaries involving some dislocation mechanisms and enhanced by segregated P atoms at finally resultant random boundaries along shear bands. The operating mechanism will be explained later in some detail. Figure 7 shows the

• fatigue. The cyclic stress-induced grain growth, accompanying the transformation of low-angle boundaries into the boundaries with higher misorientation angle, is associated with the evolution of a “diamond-shaped” grain structure along initially formed shear bands. This resulted in intergranular fatigue

Deformation-driven catalysis of nanocrystallization in amorphous Al alloys

• Rainer J. Hebert,
• John H. Perepezko,
• Harald Rösner and
• Gerhard Wilde

Beilstein J. Nanotechnol. 2016, 7, 1428–1433, doi:10.3762/bjnano.7.134

• processing route is intense deformation and nanocrystals have been shown to develop in shear bands during the deformation process. Some controversy surrounded the idea of adiabatic heating in shear bands during their genesis, but specific experiments have revealed that the formation of nanocrystals in shear

• bands has to be related to localized deformation rather than thermal effects. A much less debated issue has been the spatial distribution of deformation in the amorphous alloys during intense deformation. The current work examines the hypothesis that intense deformation affects the regions outside shear

• bands and even promotes nanocrystal formation in those regions upon annealing. Melt-spun amorphous Al88Y7Fe5 alloy was intensely cold rolled. Microcalorimeter measurements at 60 °C indicated a slight but observable growth of nanocrystals in shear bands over the annealing time of 10 days. When the cold

Lower nanometer-scale size limit for the deformation of a metallic glass by shear transformations revealed by quantitative AFM indentation

• Arnaud Caron and
• Roland Bennewitz

Beilstein J. Nanotechnol. 2015, 6, 1721–1732, doi:10.3762/bjnano.6.176

• the generation of shear bands in metallic glasses [4]. Dislocation nucleation and shear band generation are mechanisms that operate at the nanometer scale. In order to investigate the fundamental mechanisms contributing to the mechanical behavior of materials new advanced experimental techniques are

• loading rates. We discuss our results with regard to dislocation activity in crystalline materials and to the recent discussion of plasticity mechanisms in metallic glasses, including the generation of shear bands and their incipient size and indentation size effects down to the structural length scale of

• . The latter was found to be mediated by thin shear bands at moderate loads of P in the range of 400 to 1.5 µN until the sliding contact merged in a single shear zone at higher load. Note that the high shear rate parallel to the surface in those scratching experiments as compared to the slower

Influence of grain size and composition, topology and excess free volume on the deformation behavior of Cu–Zr nanoglasses

• Daniel Şopu and
• Karsten Albe

Beilstein J. Nanotechnol. 2015, 6, 537–545, doi:10.3762/bjnano.6.56

• interfaces don’t show topological disorder. Our results provide clear evidence that the mechanical properties of metallic NGs can be systematically tuned by controlling the size and the chemical composition of the glassy nanograins. Keywords: enhanced plasticity; metallic glasses; nanoglasses; shear bands

• annihilation spectroscopy [9], while molecular dynamics studies showed that glass–glass interfaces exhibit an excess free volume and a modified local order [10][11]. If plastically deformed, the soft glass in the interfaces promotes shear band nucleation similar to the effect of residual shear bands in pre

• -deformed metallic glasses [11]. Consequently, the NG exhibits a more homogeneous plastic deformation carried by a pattern of multiple shear bands [12] as compared to the bulk metallic glass (BMG), where plastic deformation is well localized in a few dominant shear bands. The influence of interfaces on the

Deformation-induced grain growth and twinning in nanocrystalline palladium thin films

• Aaron Kobler,
• Jochen Lohmiller,
• Jonathan Schäfer,
• Michael Kerber,
• Anna Castrup,
• Ankush Kashiwar,
• Patric A. Gruber,
• Karsten Albe,
• Horst Hahn and
• Christian Kübel

Beilstein J. Nanotechnol. 2013, 4, 554–566, doi:10.3762/bjnano.4.64

• twinning/detwinning processes, stress-driven grain boundary migration and the formation of shear bands [4][5][6][7]. When studying the mechanical properties of nc metals and the associated deformation mechanisms, it is important to consider the preparation technique for the corresponding bulk nc metal

Nanoglasses: a new kind of noncrystalline materials

• Herbert Gleiter

Beilstein J. Nanotechnol. 2013, 4, 517–533, doi:10.3762/bjnano.4.61

• enhanced free volume in shear bands [9][10], the average free volume content of a glass was found to increase [10][11] with increasing plastic deformation. However, despite the similarity between the microstructural features of a nanoglass produced by consolidating nanometer-sized glassy spheres and a

• nanoglass produced by introducing a high density of shear bands, the results of recent studies by molecular dynamics (MD) [12][13] and Mössbauer spectroscopy of a ball-milled melt-quenched Fe90Sc10 glassy ribbon and a Fe90Sc10 nanoglass suggest that the atomic structure of both kinds of nanoglass differ

• the nanoglass. In structurally homogenous ribbons, only one (or a few) shear bands are known to be nucleated under sufficiently high applied stresses. Plastic flow is limited to these shear bands and frequently results in fracture after an overall plastic deformation of less than 1%. However, in the