The aim of this study is to estimate the thermal diffusivity of martensitic and austenitic microstructures of a NiTi SMA. To this end, an experimental apparatus supported on the Angstrom’s method was designed, where one face of a cylindrical sample is subjected to a periodic heat flux and the other face is kept at a constant temperature. This apparatus was developed to provide the three fundamental requirements of the applied method: (1) uniformity of the thermal field in any cross section of the medium; (2) complete damping of the heat wave before it reaches the face at a prescribed temperature; (3) thermophysical properties independent of temperature within the adopted measurement range. Fourteen thermocouples are fixed at specific locations on the side of the sample, for measuring the amplitude and phase-lag of the thermal wave supplied from periodic heating at a certain frequency. The measurements of these parameters, carried out on a permanent periodic regime, are replaced into a mathematical model, in order that the thermal diffusivity can be determined by linear regression. The results obtained for the two microstructures showed good agreement with the literature, with absolute deviations below 8.5 %, proving the effectiveness of the experimental arrangement. The estimated thermal diffusivity of austenite is 48.21 % higher than that of martensite. The uncertainty quantification, assessed by the Monte Carlo Method, indicates a low dispersion, below 1.5 %, which delivers high precision and reliability to the estimated thermophysical property.

本研究的目的是估计 NiTi SMA 的马氏体和奥氏体微观结构的热扩散率。为此，设计了一种支持埃氏方法的实验装置，其中圆柱形样品的一个面受到周期性热通量的影响，而另一面保持恒定温度。该设备的开发旨在满足所应用方法的三个基本要求：(1)介质任何横截面中热场的均匀性；(2)在规定温度下，在热浪到达工作面之前完全阻尼；(3)在采用的测量范围内与温度无关的热物理特性. 14 个热电偶固定在样品侧面的特定位置，用于测量特定频率下周期性加热提供的热波的幅度和相位滞后。这些参数的测量，在一个永久的周期性制度上进行，被替换为一个数学模型，以便热扩散率可以通过线性回归确定。两种微观结构的结果与文献非常吻合，绝对偏差低于 8.5%，证明了实验安排的有效性。估计奥氏体的热扩散率比马氏体高 48.21%。由蒙特卡罗方法评估的不确定性量化表明低分散，低于 1.5%，