Magnetic field controlled superelasticity and damping properties of NiMnGa/polymer composites

Recently we have developed NiMnGa/silicone composites as prototype materials suitable for the magnetic actuation, mechanical damping controlled by magnetic field and stress sensing. The composites contain 20-30 vol. % of filler representing macroscopic and crystallographically oriented ferromagnetic martensitic particles (with spherical or irregular shape). In the present work emphasis is given to the studies of (i) dynamical mechanical response of the indicated composites subjected to the external magnetic field; and (ii) magnetically activated rubber-like behaviour of the composite.

For the first time we have observed the effect of magnetostrain in both individual particle (by the three-dimensional X-ray micro-computed tomography) and in composite as a whole (optical detection), produced by the magnetic-field-induced twin boundaries rearrangements. Strikingly, the magnetostrain response of composite (up to 4% in the field of about 0.5 T) was reversible along particle chains and in the perpendicular direction, which means an appearance of the local internal stresses driving twin boundaries back after field removal.