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Reciprocal space outside the first zone, the QES dominates the inelastic signal overwhelmingly. With the inelastic scattering signal, which remains discernible within the first Brillouin zone for specific directions in The copious stacking faults generated at the shock front introduce strong quasi-elastic scattering (QES) that competes Above the Hugoniot elastic limit (HEL), we find that The inset shows the accumulation of twinning dislocations (resulting from the absorption process) at the CTB ledge.By taking the spatial and temporal Fourier transforms of the coordinates of the atoms in molecular dynamics simulationsĬonducted using an embedded-atom-method potential, we calculate the inelastic scattering of x-rays from copper singlecrystals shocked along to pressures of up to 70 GPa. e BF-TEM image showing the fracture at the CTB ledge indicated by a black arrow. ( 1) form a pair of up-down single atomic steps see the red and blue lines inside the black rectangle. d Schematic illustration of the mechanism controlling the absorption process of the incoming curved screw dislocations (green lines): it involves the nucleation and the glide of constriction nodes in the same direction at the CTB plane as well as the backward motion of the nodes by relaxation of internal stress in the CTB after fracture. White lines show the arrangement of the twinning dislocations. The black arrow show the position of a constriction node. c Bright field TEM image obtained after fracture. White lines in b show the arrangement of the twinning dislocations in the white rectangle. White arrows indicate residual sessile dislocations left by annealing. Yellow arrows indicate the diffraction vectors while red arrows show the position of slip traces in grain B after transmission. Green arrows indicate the position of STs from the single arm sources SAS1 and SAS2. The interaction of dislocations with coherent twin boundaries (CTBs) of the type ∑3 〈110〉 CTB see extra evidence on the screw character of the incoming dislocations in Supplementary note 4.Ī and b Bright field TEM micrograph after cycle 4 showing the arrangement of the twinning dislocations resulting from the absorption process of the incoming screw dislocations at the CTB. TEM observations of the interactions between non-screw dislocations and the CTB highlight the importance of the synergy between the repulsive force of the CTB and the back stress from SASs when the interactions occur in small volumes. The coordinated motion of the twinning dislocation pairs due to the presence of the nodes leads to a unique CTB sliding mechanism, which plays an important role in initiating the fracture process at a CTB ledge. We report that the absorption of curved screw dislocations at the CTB leads to the formation of constriction nodes connecting pairs of twinning dislocations at the CTB plane in agreement with large scale 3D atomistic simulations. Here, quantitative in-situ transmission electron microscopy (TEM) observations of these mechanisms under tensile loading are performed on submicron Ni bi-crystal. However, the elementary mechanisms controlling the interaction between single arm dislocation sources (SASs), often present in nanotwinned FCC metals, and CTB are still not well understood. ![]() The introduction of a well-controlled population of coherent twin boundaries (CTBs) is an attractive route to improve the strength ductility product in face centered cubic (FCC) metals.
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