Preparation of TiNi films by diffusion technology and the study of the formation sequence of the intermetallics in Ti–Ni systems

Abstract

This study presented a novel fabrication process for TiNi thin films by vacuum diffusion technology using reactive Ni/Ti/Ni multilayer thin films. The sandwiched thin films were prepared by chemical nickel plating. Ni/Ti/Ni multilayer films were heat treated for various diffusion times and temperatures and the influences of the temperature and diffusion time on the interdiffusion behavior of the Ti-Ni system were researched in detail. The results showed that a homogeneous TiNi thin film was obtained at 1173 K with a diffusion time of 4 h. Moreover, the formation sequence of the intermetallics in the Ti-Ni diffusion system was investigated by thermodynamic analysis and experiment. It was found that three compounds -TiNi 3 , Ti 2 Ni, and TiNi -formed in the diffusion process at the Ti/Ni interfaces. More importantly, the nucleation of TiNi 3 and Ti 2 Ni was prior to that of TiNi because of the lower reaction Gibbs free energy and increasing interface energy of TiNi 3 and Ti 2 Ni.

Effects of Cu interlayers on the microstructure and mechanical properties of Al2O3/AgCuTi/Kovar brazed joints

“…The wave‐like TiFe 2 –TiNi structure did not change after the addition of Cu foil. The Gibbs free energy for the reaction between Ti and Cu to form TiCu at 900°C is −13.577 kJ/mol, which is much higher than that for the reaction between Fe, Ni and Ti . In addition, there were enough Fe and Ni atoms that dissolved from the Kovar alloy.…”

Katodik Ark Plazma İşlemi Kullanılarak Titanyum Yüzeylerinin Nikel İle Alaşımlandırılması

“…But reaction is very slow and NiTi formation has difficulties with increasing diffusion lengths and barriers. Shao et al [5,6] explained the same results from the different point of interface energies. At these studies, the last formed phase was determined as NiTi, but the first formed phase was not exactly known.…”

“…Diffusion in the binary Ni-Ti system has been the subject of a substantial number of studies aiming mainly to investigate the diffusion behavior between these two metals for powder metallurgy and brazing applications [1][2][3][4][5][6][7][8][9][10]. The major goal in these studies was to obtain and understand the mechanism of formation of the well-known NiTi phase by solid-state diffusion processes.…”

Micro-Alloying and Surface Texturing of Ti-6Al-4V Alloy by Embedding Nanoparticles Using Gas Tungsten Arc Welding

“…The XRD analyses of the Ti-6Al-4V treated layer showed the presence of three compounds at the surface: TiNi, Ti 2 Ni, and Ni/Al 2 O 3 . Evaluation of the Gibbs free energy of reaction formation indicates that the order of formation of the compounds is likely; Ti 2 Ni (72,985.9 J/Mol), followed by TiNi (61,595.3 J/Mol) [19]. The possible exothermic reaction during the surface melting and alloying is showing the following equation [20] with the sequence of formation following the same order.…”