MAGNETIC SHAPE-MEMORY MATERIAL BASED ON NICKEL, MANGANESE, GALIUM, COBALT AS METAL STRIPS ULTRA-FAST SOLIDIFIED FROM MELT AND PROCESS FOR PREPARING THE SAME

The invention relates to magnetic materials with shape memory as metal strips based on Ni-Mn-Ga, with and without Co doping, and to a process for preparing the same, the materials being meant to be used as active elements in micropumps integrated in portable fluid systems for the transport of fluid volumes in the range of nanoliters and picoliters. According to the invention, the materials have a strongly textured martensitic structure and the following composition expressed in atomic percentage : a. Ni48Mn29Ga20Co3 with commutation magnetic field of 0.073 T, coercivity of 0.0064 T, magnetization of 65.87 emu/g at 1 T and deformation of 49x10-6 in radial multidirectional magnetic field of 0.4 T, and b. Ni49Mn32Ga19, with commutation magnetic field of 0.047T, coercivity of 0.028 T, magnetization of 40.63 emu/g at 1 T and deformation of 36x10-6 in radial multidirectional magnetic field of 0.4 T, all values being measured at the ambient temperature of 20°C. According to the invention, the process consists in melting, repeated four times, the metal constituents with a purity of 99.99% in an electric arc furnace, in a protective Ar atmosphere with a purity of 99.99% to ensure the homogeneity of the material, followed by remelting the alloys in quartz tubes positioned among the coils of the inductor through which the radio frequency current flows and ejecting them, with an overpressure of 0.45 at of 99.99% purity Ar, through the 3 mm-long and 1 mm-wide rectangular slot thereof, directly onto the water-cooled Cu rotary drum for ultra-fast solidification, followed by a heat treatment for 1 hour, at a temperature of 400°C, in a vacuum atmosphere of 10-6 mbar. Invenţia se referă la materiale magnetice cu memoria formei sub formă de benzi metalice pe bază de Ni - Mn - Ga cu şi fără dopaj de Co şi la un procedeu de obţinere a acestora, materialele fiind utilizate ca elemente active în micropompe integrate în sisteme fluidice portabile pentru transportul volumelor fluidice de ordinul nanolitrilor şi picolitrilor. Materialele conform invenţiei au o structură martensitică puternic texturată şi următoarea compoziţie exprimată în procente atomice: a) Ni48Mn29Ga20Co3, cu câmp magnetic de comutare de 0,073 T, coercitivitate de 0,0064 T, magnetizare de 65,87 emu/g la 1 T şi deformare de 49 x 10-6 în câmp magnetic multidirecţional radial de 0,4 T, şi b) Ni49Mn32Ga19, cu câmp magnetic de comutare de 0,047 T, coercitivitate de 0,028 T, magnetizare de 40,63 emu/g la 1 T şi deform