Crystal orientation and grain boundary effects on plastic deformation of FCC particles under high velocity impacts

Material plastic behavior during deformation is affected by several parameters such as atomic structure, crys-talline orientation, grain boundaries, impurities etc. In this study, molecular dynamic simulations were performed to provide a detailed understanding of the effects of grain orientation and grain boundaries on plastic deformation of FCC particles under high velocity impacts. Two single-crystal particles with different crystalline orientations, two simple polycrystal particles (bicrystal, and tricrystal) with inner walls parallel and perpendicular to the shock wave, and a polycrystal particle with 64 random grains were modeled. The results showed that the deformation behavior and microstructural evolution depended directly on their initial microstructure of the particles, whereas the resulting shear strain pattern was the same for all the particles. Phenomena such as recovery, crystallization, recrystallization, grain growth, twining, and grain rotation were observed during the deformation of the particles. In addition, it was shown that heterogeneous nucleation of Shockley partial dislocations was the main mechanism at the onset of the deformation. Another important deformation mechanism was solid-state amorphization due to the densification of the dislocation network in certain regions of the particles, also associated with thermal softening effects. (AU)