Ni–Ti-Hf high-temperature shape memory alloy: Measure of the Clausius-Clapeyron coefficient through mechanical spectroscopy

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. •Internal friction on a Ni–Ti-Hf High-Temperature Shape Memory Alloys.•Martensitic transformation on a Ni–Ti-Hf High-Temperature Shape Memory Alloys.•Anomalous pre-martensitic softening measured on a Ni–Ti-Hf Shape Memory Alloy.•Mechanical Spectroscopy allows measuring the Clausius-Clapeyron coefficient.