Dependence of dislocation creation on tensile orientation in face-centered-cubic ductile metals under high strain rate loading

We investigate through molecular dynamic simulations the dependence of dislocation creation on tensile orientation in face-centered-cubic ductile metals under high strain rate loading. It is found that while dislocations generally originate from the double-layer defect clusters consisting of flatted octahedral structures (FOSs), the formation mechanism and the types of FOSs, as well as the types of nucleated dislocations, depend on the applied loading directions. For the loading along the [(1) over bar 10]; [1 (1) over bar2], and [111] crystal directions, it is shown that a pair of the nearest-neighboring atoms move away to form the elongated FOS. However, for the loading along the [100] crystal direction, a pair of the next-nearest-neighboring atoms move close to form the compressed FOS. According to the uniform deformation amount of the spacing vector for a pair of neighboring atoms and the stress component along the Burgers vector on the stacking fault plane, we analytically predict the activated types of FOSs and dislocations for different loading directions, which turn to be remarkably consistent with our numerical simulations. (C) 2015 AIP Publishing LLC.