Comment on the paper "Thermal diffusivity of Ni-Ti SMAs" by C. Zanotti, P. Guliani, G. Riva, A. Tussi, A. Chrysnathou
2010
Abstract
Zanotti et al. used the mathematical model for the determination of the thermal diffusivity that was based on the 1D unsteady heat diffusion equation. They found a drastic decrease and then increase of the thermal diffusivity in the transformation temperature range.
This negative peak, however, has no physical meaning because the general heat conduction equation was derived and solved with boundary conditions that require that no phase transformations occur in the material. The latent heat changes the temperature distribution in the sample, so selected model cannot be applied in the transient temperature range.