Oxidation behavior of TiNi-Pd shape memory alloys

The oxidation behavior of TiNi, TiNiPd and the Ce-containing TiNiPd shape memory alloys are investigated using thermogravimetric analysis, X-ray analysis, scanning electron microscopy and electron probe microanalysis. It has been found that the oxidation scale of the alloys exhibits different sub-layers. Generally, the outmost layer is mainly composed of rutile TiO2. The TiNiO3 phase exists for all the alloys, and the Ti4Pd2O phase for TiNiPd alloys as well. These oxides act as important media during the ion exchanging process during the oxidation and cause different oxidation resistance. The addition of Ce in the TiNiPd alloy effectively impedes the Ti ions outward diffusion, causes a wide distribution of Ni and Pd over the scale depth, and obviously improves the oxidation resistance.