Electrochemical Codeposition and Heat Treatment of Nickel-Titanium Alloy Layers

Abstract

The fabrication of nickel-titanium (Ni-Ti) alloy layers via the electrochemical codeposition and heat treatment is proposed and investigated herein. The codeposition of a Ti-dispersed Ni-matrix layer on an indium tin oxide-coated glass substrate was systematically conducted over varied current densities, Ti-particle loadings in an electrolyte and Ti particle sizes to investigate their effects on the Ti content and morphology of the layers. A moderate particle loading of approximately 2 to 6 g/dm3 led to relatively high Ti contents, whereas a decrease of particle size gave a dense and uniform layer with relatively low Ti contents. Following heat treatment, the Ni-Ti composite layers completely transformed into the Ni-Ti alloys with varying dominant phases of NiTi, Ni3Ti, and Ni solid solution depending on the alloy compositions. The assessment of the Ni-Ti phase diagram and the Ni-Ti interdiffusivity are discussed to verify the resultant phases present in the post-annealed layers. The results and analyses from this work entail the construction of the codeposition’s mechanistic views and the interaction of the hydrodynamic, gravitational, and electrophoretic forces on particles suspended in an electrolyte, which are critical to the development of the Ni-Ti component fabrication via the combined codeposition-heat treatment route.