Flow stress of Ni-rich NiTi thin films

Abstract

The flow stress of thin films of nickel-rich, NiTi shape memory alloys were studied. NiTi thin films were deposited onto copper substrates by magnetron sputtering in an argon atmosphere using a sputtering target of an equiatomic TiNi alloy. The grain size of the NiTi thin films was obtained using scanning electron microscopy. The strength of polycrystalline thin films were found to depend on both their grain size and their thickness. The stress-strain curves of the free-standing NiTi thin films were obtained from the stress-strain curves of copper substrate together with the thin film adherent to the substrate compared with the stress-strain curves of copper substrate without film.