Phase Transformation and Shape Memory Effect of Ti–Pd–Pt–Zr High-Temperature Shape Memory Alloys
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To understand the potential of high-temperature shape memory alloys, we have investigated the phase transformation and shape memory effect of Ti–(50 − x)Pt–xPd–5Zr alloys (x = 0, 5, and 15 at.%), which present the B2 structure in the austenite phase and B19 structure in the martensite phase. Their phase transformation temperatures are very high; A f and M f of Ti–50Pt are 1066 and 1012 °C, respectively. By adding Zr and Pd, the phase transition temperatures decrease, ranging between 804 and 994 °C for A f and 590 and 865 °C for M f. Even at the high phase transformation temperature, a maximum recovery ratio of 70% was obtained for one cycle in a thermal cyclic test. A work output of 1.2 J/cm3 was also obtained. The recovery ratio obtained by the thermal cyclic test was less than 70% because the recovery strain was < 1% and a large irrecoverable strain was obtained. The shape recovery was explained by the austenite strength. The training effect was also investigated.
KeywordsShape memory alloys Titanium platinum Martensitic transformation Strain–temperature test Work output
This research was supported in part by the Japan Society for the Promotion of Science (JSPS) through the “Funding Program for Next Generation World-Leading Researchers (NEXT Program),” initiated by the Council for Science and Technology Policy (CSTP). The authors wish to thank Mr. M. Nishio at NIMS for the EMPA analysis.
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