Effect of heat treatment on tensile deformation behavior of Ni-Co film/Fe substrate systems

The effects of heat treatment on microstructure and tension property of Ni-Co film/Fe substrate systems were investigated. The deformation and fracture morphologies of Ni-Co films/Fe substrate systems were studied by in-situ scanning electron microscopy (in-situ SEM) before and after heat treatment. The results show that a Ni-Co/Fe diffusion layer appears between the film and substrate after heat treatment; the elongation of film/substrate system increases with increasing the heat treatment temperature. Both the strength and ductility of the film/substrate system are preferable when heat treatment temperature is 650 °C, meanwhile the maximum elongation is up to 46%. During tensile deformation, the deformation behaviors of Ni-Co film/Fe substrate are quite different before and after heat treatment. The samples after heat treatment went through the progress of holes' emergence, growth and extension, whereas the samples without heat treatment accompanied with no holes, just cracked instead, showing that appropriate heat treatment is helpful to improve the toughness of material, and mechanical properties.