Likhachev A. Irreversible Thermodynamics of Martensitic Transformation in Alloys with Thermally and Magneticly-Induced Shape Memory Effects

The present thesis is devoted to some actual investigations in the field of martensitic transformation thermodynamics in both the traditional non-magnetic materials and the recently discovered new ferromagnetic materials able to show the magnetic field-induced twinning strain phase. The basic thermo- and magnetic field-induced state equations for the martensite fraction dependence on the temperature and pressure and the strain dependence on the magnetic field and external stresses have been directly derived from the energy conservation principle taking into account an additional internal work performed due to the irreversible austenite-martensite or twin interface motion. These relationships were used for the practical thermodynamical calculations in CuZnAl, CuAlNi, NiTi alloys, an also to quantitively estimate the giant magnetic field induced strain and superelastic behavjor effects and also for the mechanical work output estimation, its optimization and finding the optimal energy conversion factor for the Ni-Mn-Ga magnetic shape memory alloys.