Thermal diffusivity of Ni–Ti SMAs

Abstract

In this paper thermal diffusivity dependence on temperature of NiTi SMAs alloy in the range from 300 K up to 1500 K is reported and the experimental–numerical approach adopted for this scope is described. The experimental work is based on the capability to heat the NiTi sample by means of laser radiation and to record the temperature history at different positions of the sample and afterwards on the possibility to reproduce the experimental curves by numerical computations. A variety of heating rates ranging from 2 K/s to 100 K/s and maximum temperature values (600–1500 K) at the top of the NiTi sample, were used to carry out experiments featured by different heating transients. The numerical code, based on the 1D unsteady heat diffusion equation, was observed to be in very good agreement with the experimental results and the thermal diffusivity value that was obtained showed drastic changes during the phase transition that occurred during the martensitic transformation.