Diffusion evaluation of Cu in NiTi Bi-layer thin film interface

作者：Mohri Maryam; Nili Ahmadabadi Mahmoud^*; Flege Stefan

来源：Journal of Alloys and Compounds, 2014, 594: 87-92.

DOI：10.1016/j.jallcom.2014.01.068

• Diffusion
• Cu
• NiTi thin films
• Compositional gradient

NiTi alloys are shape memory alloys (SMAs) which combine two very unique properties, shape memory effect and super-elasticity. These properties depend strongly on the composition and structure. %26lt;br%26gt;In this research volume diffusion of Cu in bulk Ni50.8Ti49.2 alloy with B2 ordered structure has been measured and diffusion phenomenon on a bi-layer Ni-Ti thin film was also studied. The penetration profiles were determined by two techniques: secondary ion mass spectroscopy (SIMS) and energy dispersive X-ray analysis (EDS). Cu diffusivity in NiTi-Ni rich bulk was found to follow linear Arrhenius dependencies with the pre-exponential factor of 5.8 +/- 1 x 10(-14) m(2)/s and the activation energy of 40 +/- 4 kJ/mol. Anti-site defect diffusion mechanism is suggested to provide diffusion of copper in NiTi alloy. The diffusion coefficient of Cu in Ni-Ti Ni-rich was used to estimate the gradient composition in the bi-layer thin film (Ni-rich/NiTiCu) after annealing. The bi-layer thin film was deposited on Si (111) using DC magnetron sputtering and annealed at 773 K for 1 h. The crystallization temperature and microstructure of the thin film were characterized using differential scanning calorimeter (DSC) and X-ray diffractometer (GIXRD). The results depicted that estimation of the concentration gradient in the bi-layer thin film using the diffusion equation obtained from the NiTi bulk samples shows good agreement with the measured concentration gradient in the bi-layer.

• 出版日期2014-5-5