Shape memory behavior of Ni-Fe-Ga and Ni-Mn-Sn ribbons

Magnetic Shape Memory Alloys exhibit multifunctional properties due the martensitic transformation (MT) and accompanying changes in the magnetic subsystem. In this work, melt spun ribbons of nominal composition Ni 55 Fe 16 Ga 29 (R1) and Ni 50 Mn 40 Sn 10 (R2) have been produced and characterized by the calorimetric, thermomechanical, mechanical, microscopic and X-ray measurements. The effect of short annealing on MT and thermo-mechanical properties is rather modest and in the case of R2 enhances its brittleness. R1 and R2 as-spun ribbons show MT at T M ~ 340 K and ~ 420 K, respectively. The strain-stress curves for Ni-Fe-Ga in austenitic phase indicate good visco-elastic properties, although the superelastic effect was not well pronounced. Ni-Fe-Ga as-cast and annealed samples, as well as the as-cast Ni-Mn-Sn ribbons, present a shape memory effect with an anomalous contraction and elongation at low external stresses in the course of the forward and reverse MT, consequence of the compressive internal stresses.