1 Synthesis, Microstructure and Properties of Metallic Materials with Nanoscale Growth Twins

We have recently synthesized 330 stainless steel thin films and bulk Cu foils via magnetron sputtering with an average twin spacing of ~ 5 nm. Twin interfaces in both systems are of {111} type and normal to the growth direction. The hardness of sputtered materials is an order of magnitude higher than that of their bulk counterparts. Growth twins with such high twin density and preferred orientation are rarely seen in elemental metals. Sputtered Cu foils exhibited tensile strengths of 1.2 GPa, a factor of 3 higher than that reported earlier for nanocrystalline Cu, average uniform elongation of 1-2 % and ductile dimple fracture surfaces. This work provides a new route for the synthesis of ultra-high strength, ductile metals via control of twin spacing and twin orientation in vapor-deposited materials