coherent and incoherent twin boundary

1. Strain hardening and softening in nanotwinned Cu:

Nanotwinned Cu foils with about 99% coherent twin boundaries (TBs) among all the boundaries were made. These coherent

TBs, with an average spacing of 25 nm, were engineered approximately parallel to foil surfaces. Low plane-strain deformation

enhances the hardness by refining microstructure and introducing dislocations. High plane-strain deformation results in crystallographic

lattice rotation and reaction between dislocations and coherent TBs, and induces incoherent TBs, thus twin coarsening and