Characteristics of TiNi shape memory foils manufactured by double cathodes electrochemical polishing

TiNi shape memory foils up to 25μm thickness are fabricated by electrochemical polish thinning with double copper cathodes. The use of double cathodes at the same time can shorten the polish time and alleviate the over-etching pitting and edge etching attack effect to produce two smooth sides. The surface morphology results that the grains of the as-hot rolled foil are elongated along the rolling direction but that of the electrochemical polished ones are equal-axial with an average grain size of about 8.5 μm. Both the martensitic transformation temperature and transformation enthalpy of the foils decrease with the decrease of the thickness because thinner foils possess relative larger volume ratio of the oxide layers which cause the chemical composition shift and inhibit the martensitic transformation.

Keywords: TiNi shape memory alloys; Foils; Electrochemical polish thinning; Thickness effect.