Microstructural evolution and surface strengthening of pulse-laser treated Ti/Ni multilayer thin films

In this study, a picosecond pulse laser was utilized to treat Ti/Ni multilayer thin films to induce desired microstructure change and surface strengthening. It was observed that with the increase of laser pulse-energy, the microstructure of the treated films can be significantly modified. The surface morphology evolves from a homogeneous grain surface, to a cross-hatched pattern surface, and then to a rough melted surface covered with bubbles, voids and cracks. And the cross-section morphology evolves from a multilayered structure to partially intermixed and eventually fully intermixed structure. Due to the precipitation of Ti–Ni intermetallic phase, laser treatment with high pulse-energy led to surface strengthening on Ti/Ni multilayer thin films.