Microstructures and transformation characteristics of thin films of TiNiCu shape memory alloy

Both sputtering conditions and crystallizing temperatures have great influence on the microstructures and phase transformation characteristics for Ti(51)N(4)4Cu(5). By means of the resistance-temperature measurement, X-ray diffraction and atomic fore microscopic study, the results indicate that the transformation temperatures of the thin films increase and the "rock candy" martensitic relief is more easily obtained with promoting the sputtering Ar pressure, sputtering power, or crystallizing temperature. However, when sputtering Ar pressure, sputtering power, or crystallizing temperature are lower, a kind of "chrysanthemum" relief, which is related with Ti-rich GP zones, is much easier to be observed. The reason is that during crystallization process, both of the inherent compressive stresses introduced under the condition of higher sputtering pressure or higher crystallizing temperature are helpful to the transition from GP zones to Ti-2 (NiCu) precipitates and the increase of the transformation temperatures. The addition of copper to substitute for 5 % nickel in mole fraction can reduce the transformation hysteresis width to about 10 similar to 15 degreesC.