Shear band formation and ductility in nanotwinned Cu

The ductility and plastic flow behavior of highly aligned nanotwinned copper produced by interrupted magnetron sputtering is investigated. Tensile tests were performed at various strain rates at both room and liquid nitrogen (77 K) temperatures. Higher ductility and strength are reported for all samples tested at 77 K. The observed inhomogeneous deformation and shear band propagation are discussed as functions of the testing temperature, decreasing heat capacity at 77 K and low initial dislocation density, which leads to a yield peak.