Abstract:

The martensitic transition temperature and thermal hysteresis temperature in Ni_51.5Mn₂₄Ga_24.5singlecrystalline and Ni_47.5Mn_27.5Ga₂₅ polycrystal were investigated by means of AC magnetic susceptibility. According to the boundary frication phenomenological theory, the energy was calculated consumed for phase boundary motion in these free samples during martensitic transformation. It has been found that the energy consumed for phase boundary motion is 19.96 J/mol and 34.93 J/mol, respectively, which is only a small part of the latent heat of martensitic transformation. Furthermore, omparative thermodynamic parameter indicated that thermal hyseresis of martensitic transformation originates from the friction of phase boundary motion, which in turn accounts for the thermal hysteresis during transformation in Ni-Mn-Ga alloys quite well.

Key words: phase boundary friction
, thermal hysteresis, martensitic transformation