Mixing behaviors in Cu/Ni and Ni/V multilayers induced by cold rolling

Multilayers of Cu60/Ni40 and Ni70/V30 foil arrays were cold rolled in order to study the transformation reactions and mixing behaviors induced by deformation. Upon cold rolling, the layer thicknesses were refined to about 20 nm and solid solution phases were induced from pure end members (i.e. Cu, Ni and V) in both cases. The composition profiles for Cu/Ni and Ni/V multilayer samples at the deformation level where the solid solution phases coexist with end members were investigated by means of atom probe tomography and electron energy loss spectrum, respectively. An oscillation in the composition of Cu-Ni solid solution phase was observed, however the composition profile of Ni/V shows a smoothly varying curve between the end members. The effective diffusion coefficients were promoted by about 30 orders of magnitude for both Cu/Ni and Ni/V compared to room temperature diffusion. The effective temperature for Cu/Ni multilayers after 36 passes and Ni/V after 60 passes are estimated as 946 K and 936 K respectively.