Characteristic of specific heat capacity of NiTi alloy phases①
(School of Materials Science and Engineering, Shanghai Jiaotong University,Shanghai 200030, P.R.China)
Abstract: The specific heat capacity of NiTi alloy at constant pressure using MDSC (Modulated differential scanning calorimeter) was determined. It was found that the variation tendencies of the specific heat capacity for different phases are different. The fitting equations of the specific heat capacity for martensite and austenite phases were presented. Then,a reason, based on thermodynamic point of view, was proposed to explain the difference of the specific heat capacity between martensitic and austenitic phases. Finally, compared with the specific heat capacity of pure Ni and Ti, it was found that the specific heat capacity of NiTi alloy is inherent to that of pure Ti. When the specific heat capacity of NiTi alloy is calculated by Neuman-Kopp, in the temperature region of phase transformation and the temperature higher than 400 K, the results are not desirable.
Key words: specific heat capacity; NiTi; phase transformation; thermodynamic