Landau-energy landscape reconstruction for a Ni-Fe-Ga(Co) Shape Memory Alloy

Abstract: In the framework of continuum mechanics, the thermo-mechanical behavior of shape memory alloys is often described using the Landau-theory approach, where the multi-well free energy density of the crystal is approximated by a polynomial with the required number of minima and energy barriers. Here we show how the energy landscape (in the strain-temperature space) can be reconstructed from experiments, and how accurately this energy is approximated by the Landau-theory ansatz. Elastic behavior of single crystals of Ni-Fe-Ga(Co) ferromagnetic shape memory alloys is studied in a broad temperature range. Using tensile stress-strain measurements and ultrasonic characterization, we prove that austenite and martensite phases of the given alloy exhibit strongly non-linear elastic responses, and we utilize the non-linear stress-strain data for constructing an energy function describing the observed behavior in the context of the Landau theory. We discuss the implications of the constructed model, focusing in particular to the so-called critical point in the energy landscape, where the austenite-martensite transition becomes weakly second-order.

MathematicsPhysics

Audience: researchers in the topic

Nečas Seminar on Continuum Mechanics

Series comments: This seminar was founded on December 14, 1966.

Faculty of Mathematics and Physics, Charles University, Sokolovská 83, Prague 8. If not written otherwise, we will meet on Mondays at 15:40 in lecture hall K3 (2nd floor).