Abstract
In this study, the thermal cyclic properties of Ti-(50-x)Pd-xPt-5Zr alloys (x = 5, 15, 25, at%), comprising B2 and B19 structures in austenite and martensite, were investigated by a thermal cyclic compression test under a constant load of between 15 and 200 MPa. The transformation temperature measured using differential scanning calorimetry increased with increasing Pt concentration. The highest austenite finishing (Af) temperature, 648 °C, was obtained in the Ti-25Pd-25Pt-5Zr alloy. Irrecoverable strain due to thermal cyclic testing was observed during each test, even at a stress of 50 MPa. The work output, calculated as the product of the transformation strain and the applied stress from strain–temperature curves, decreased with increasing Pt concentration. This was because of the lower strength of the austenite phase due to Af increasing with an increase in the concentration of Pt. Although irrecoverable strain was observed with the first thermal cycle test, it decreased after several thermal cyclic tests, which are called training.
Highlights
Shape memory alloys (SMAs) are useful materials for actuators
SMAs are expected to be used at high temperatures, i.e., 200–800 ◦ C, in automotive and aerospace applications to increase the thermal efficiency of engines [2]
X-ray diffraction (RINT-TTR III, Rigaku Co., Tokyo, Japan) measurements were conducted for solution-treated samples at room temperature and at 700 ◦ C using CuKα radiation at 50 kV and Specimens of 4 mm in diameter and 1 mm in height were cut for differential scanning calorimetry (DSC)
Summary
Shape memory alloys (SMAs) are useful materials for actuators. Ti-Ni-based SMAs are currently used in temperature-sensitive devices [1]. Ti-Ta-based β-Ti alloys have been investigated as potential high-temperature SMAs [11]. Ti-Pt [21,22,23,24,25], the addition of alloying elements has been attempted; this process is reviewed in [26,27,28]. It was found that an alloying element has some effect at improving the strength of the austenite and martensite phases, resulting in improved shape recovery. In most cases, the MTT decreases when alloying elements are added. Zr and Pd were simultaneously added to Ti-Pt to improve shape recovery and control MTT [29]. The effect of Pt addition to Ti-50Pd-5Zr on the MTT and shape recovery was investigated
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