Functionally grading the shape memory response in NiTi films: Laser irradiation

A new process and mechanism are presented for controlling the shape memory response spatially within monolithic NiTi thin film structures. This technique is shown to effectively control the martensitic phase transformation temperature and exhibits control over aspects of the mechanical and shape memory responses as well. Specifically, the martensitic phase transformation temperature decreases with incident laser energy density. Concomitant modifications are observed in both the mechanical and shape memory responses in laser processed films. Analysis and characterization are performed via temperature controlled optical microscopy, x-ray diffraction, atomic force microscopy, and nanoindentation.