Effect of the cooling rate on the thermal and thermomechanical behavior of NiTiHf high-temperature shape memory alloy


Akgul O., Tugrul H. O. , KOÇKAR B.

JOURNAL OF MATERIALS RESEARCH, cilt.35, sa.12, ss.1572-1581, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 35 Konu: 12
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1557/jmr.2020.139
  • Dergi Adı: JOURNAL OF MATERIALS RESEARCH
  • Sayfa Sayıları: ss.1572-1581

Özet

In this study, the effect of the cooling rate on the thermal and thermomechanical behavior of NiTiHf high-temperature shape memory alloy was studied by differential scanning calorimetry and via running isobaric thermal cycling experiments. The cooling rates were set to 5, 10, and 15 degrees C/min for each cycle in both experiments, while the heating rate was kept as 10 degrees C/min. It was found that the transformation temperatures and thermal hysteresis values do not depend on the change in the cooling rate. On the other hand, the austenite to martensite transformation enthalpy as measured from DSC analyses increases with the increase in the cooling rate due to the higher measurement sensitivity at higher scanning rates. Recoverable strain values which were determined from isobaric thermal cycling experiments do not differ since the transforming volume does not change with the change of the cooling rate. All these findings are explained based on the fundamental thermodynamical approach.