The effect of nanoscale twin boundaries on fracture toughness in nanocrystalline Ni.

Nanoscale twin boundaries (TBs) were recently reported to be capable of enhancing the fracture toughness of nanocrystalline (nc) metals. The present study aims to investigate the toughening effects of nanoscale TBs in nc Ni by using molecular dynamics (MD) simulation. It is shown that the presence of embedded nanoscale TBs facilitates the accommodation of dislocations through partial dislocation motion along TBs, resulting in improved fracture toughness. Moreover, crack propagation is observed to be intragranular in a nanotwinned sample, concurrent with nucleation of nanovoids in the intersections of TBs and grain boundaries (GBs).