Structures and defects induced during annealing of sputtered near-equiatomic NiTi shape memory thin films

Abstract

Structures and defects induced during annealing were studied in free-standing NiTi thin films produced by rf magnetron sputtering. Ni4Ti3 precipitates coherent with the (B2) matrix do not affect the shape memory behavior of the thin films annealed at 550°C for short times. With the further increase of the annealing time and/or temperature, less coherent Ni4Ti3 precipitates develop and hinder the shape memory behavior. The embrittlement of the annealed films probably results from grain-boundary precipitation, thermal etching, and stress gradients. © 1996 American Institute of Physics.