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Laser Annealing of Amorphous NiTi Shape Memory Alloy Thin Films to Locally Induce Shape Memory Properties
Xi Wang, Yves Bellouard, Joost J. Vlassak
Published in Acta Materialia 53 (2005) p4955-4961.
Abstract — We present the results of a crystallization study on NiTi shape memory thin films in which amorphous films are annealed by a scanning laser. This technique has the advantage that shape memory properties can be spatially distributed as required by the application. A kinetics study shows that nucleation of the crystalline phase occurs homogenously in the films. Consequently, the laser annealing process produces polycrystalline films with a random crystallographic texture. The crystallized films have a uniform microstructure across the annealed areas. The material in the crystalline regions transforms reversibly to martensite on cooling from elevated temperature and stress measurements show that a significant recovery stress is achieved in the films upon transformation.