Precipitate strengthening and thermal stability in three component metallic nanolaminate thin films

Cu/Ni/Nb tri-layer and CuNi/Nb alloy multilayer films were annealed to examine the microstructural evolution and mechanical properties of three component laminated metallic nanostructures. Scanning transmission electron microscopy showed Ni_xNb_y compounds forming on either side of the Nb layer in both tri-layer and alloy films. Post annealing nanoindentation showed all annealing conditions resulted in increased hardness, indicative of the Ni_xNb_y intermetallic phase increasing the hardness of the films. The hardness of both films achieves a maximum hardness after annealing for 3 h at 300 °C. The hardness increase as the annealing temperature increases corresponds to a thicker Ni_xNb_y layer at the incoherent boundary. This strengthening technique could be implemented in a variety of different multilayer systems to achieve age-hardenable multilayer metallic nanostructures.