Estimation of Thickness Ratio of Bi-layer TiNi to Enhance Shape Memory Behavior

摘要

Shape memory thin films deposited by sputtering are attractive candidates for micro-electro-mechanical-system (MEMS) because of their large deformation and strong recovery force. In the present study Ni-Ti thin films have been deposited on NaCl substrates by DC magnetron sputtering source fitted with an 80mm diameter alloy target. In order to obtain a variety of film compositions, several discs of alloy target, which prepared in vacuum arc remelting (VAR), were used. Three types of thin films have been deposited; Ti and Ni-rich thin films were separately deposited on NaCl substrate and also a composite layer of Ni45Ti50Cu5 and Ni-rich. The as deposited Ni-Ti thin films were crystallized to change the amorphous structure to a nano-structured material to characterize shape memory and superelastic behaviors. The effect of composition on film structure and mechanical behavior was studied by using X-ray diffraction (XRD) and nanoindentation. The results of thin films behavior were used to calculate the thickness ratio of be-layer composite NiTi to obtain enhanced shape memory behavior.