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. (C) 2020 The Author(s). Published by Elsevier B.V.

Automated summary

The martensitic transformation of Ni49.5Ti35.5Hf15 high temperature shape memory alloy was characterized by internal friction measurements, revealing reversible B2 <-> B19' transformations and anomalous pre-martensitic softening in the high-temperature phase. A new method for measuring the Clausius-Clapeyron coefficient through mechanical spectroscopy, based on internal friction spectra analysis, was proposed for non-destructive testing and potential development of advanced prototypes of shape memory alloys.