Abstract
In this study, we have achieved an enhancement in the corrosion fatigue life using the thermal oxidation treatment technique that can generate a passive film on the surface of the TiNi shape memory alloy wire. The procedure for the thermal oxidation treatment is explained as follows. First, the as-received material with oxide film was mechanically polished to remove the film by abrasive paper and a buffing compound. Second, the material was heat treated in the electrical furnace filled with N_2-20 vol% O_2 gas. The heat treatment was carried out for 1 hour at 673 K and subsequently cooled in the furnace. The results obtained can be summarized as follows: (1) The passive film is uniformly generated on the surface of the TiNi shape memory alloy wire by the thermal oxidation treatment on a macroscopic scale and has a noteworthy effect on the improvement of the corrosion resistance characteristics. (2) The corrosion fatigue life of the thermal oxidation treatment is longer than the material that was heat treated in air. We found that the film generated by the thermal oxidation treatment can maintain the adhesion to the base material even when subjected to a bending strain of more than 1%.
