Twin stabilization in a ferromagnetic shape memory alloy

The modulus and damping of martensitic Ni49Mn26Ga25 (wt.%) cantilevers that deform by twin motion when bent have been investigated at room temperature. The modulus increases logarithmically as a function of aging time while the damping decreases commensurably. Both changes signal a gradual reduction of the twin boundary mobility. The logarithmic time dependence indicates a wide distribution of relaxation times. This distribution results from the volume dependence of the adaptation kinetics of nano-sized short range ordered clusters to the martensitic symmetry.