Abstract The martensitic transformation of Ni49.5Ti35.5Hf15 high temperature shape memory alloy is characterized by internal friction measurements. The temperatures for the reversible B2 ↔ B19’ transformation appear in the range 410−479 K on cooling and 447−526 K on heating. In addition, a strong anomalous pre-martensitic softening of the dynamic modulus is reported in the high-temperature phase, between 850 K and 550 K, evidencing the thermoelastic character of this family of alloys. Based on the analysis of the internal friction spectra, a theoretical and experimental methodology is proposed to measure the Clausius-Clapeyron coefficient through mechanical spectroscopy. This new non-destructive method could be extremely useful for the development of advanced prototypes of shape memory alloys.

中文翻译：

---

Ni-Ti-Hf 高温形状记忆合金：通过机械光谱测量克劳修斯-克拉珀龙系数

摘要 Ni49.5Ti35.5Hf15高温形状记忆合金的马氏体转变通过内摩擦测量表征。可逆 B2 ↔ B19' 转变的温度出现在冷却时 410-479 K 和加热时 447-526 K 的范围内。此外，据报道，在 850 K 和 550 K 之间的高温阶段，动态模量发生了强烈的异常预马氏体软化，证明了该系列合金的热弹性特性。在分析内摩擦谱的基础上，提出了一种通过力学谱测量克劳修斯-克拉佩龙系数的理论和实验方法。这种新的非破坏性方法对于开发先进的形状记忆合金原型非常有用。