RECENT IMPROVEMENTS IN CONDUCTION CALORIMETRY - APPLICATION TO THE MARTENSITIC TRANSFORMATIONS IN SHAPE-MEMORY ALLOYS

A critical reading of the work of Tian and Calvet and the actual state of the art in thermostats, temperature control and the modelling of d ifferential conduction calorimeters suggest a backwards evolution to n on-differential calorimeters. An elementary design shows increased per formances at constant temperature; the sensitivity is 700 mV W-1 at ro om temperature, the short-term noise around 200 nV approximate to 0.3 mu W, and the baseline fluctuations around 1 mu V approximate to 1 mu W. Measurements of the dissipated heat power, indicative of the intern al processes after a heat treatment (different types of quench) were r ealised for a Cu-Zn-Al shape memory alloy. The experimental results es tablished that the dissipated heat evolves in time for at least 2 or 3 days. At least two time constants were detected and, as expected, the values are dependent on the quench type and sample mass.