Ultraslow calorimetric studies of the martensitic transformation of NiFeGa alloys: detection and analysis of avalanche phenomena

Abstract

We study the thermal properties of a bulk Ni55Fe19Ga26 Heusler alloy in a conduction calorimeter. At slow heating and cooling rates (1K/h), we compare as-cast and annealed samples. We report a smaller thermal hysteresis after the thermal treatment due to the stabilization of the 14M modulated structure in the martensite phase. In ultraslow experiments (40mK/h), we detect and analyze the calorimetric avalanches associated with the direct and reverse martensitic transformation from cubic to 14M phase. This reveals a distribution of events characterized by a power law with exponential cutoff $p(u)\propto u^{-\epsilon }\exp (-u/\xi )$ where $\epsilon \sim 2$ and damping energies $\xi =370$uJ (direct) and $\xi =27$uJ (reverse) that characterize the asymmetry of the transformation.

13 pages; 6 figures; 3 tables

References in corpus (3)

• Power-law distributions in empirical data
• On the asymmetry of the forward and reverse martensitic transformations in shape memory alloys
• Thermo-magnetic characterization of phase transitions in a Ni-Mn-In metamagnetic shape memory alloy

Cited by in corpus (1)

• Phase dependence of the Thermal Memory Effect in Polycrystalline Ribbon and Bulk Ni55Fe19Ga26 Heusler Alloys