Effect of directional solidification on magnetic-field-induced strain in Ni-Mn-Ga-RE(RE = Tb, Sm) alloys

The polycrystalline Ni-Mn-Ga-RE(RE = Tb, Sm) alloys with oriented crystal structures were prepared by the technique of directional solidification. Investigations were made on the effects of oriented crystal structures on the magnetic-field-induced strains of the alloys. The experimental results show that the oriented crystal structures increase remarkably the magnetic-field-induced strains of the magnetic shape memory alloys. As the magnetic field with the same magnitude was applied, the strain values of the directional solidification samples were higher than those of as-east samples. Especially in a strong magnetic field ( > 0.5T), the strain values of the samples with oriented crystal structures are twice as large as those of the as-cast samples with the same composition. Therefore, the technique of directional solidification is an effective way to prepare the oriented Ni-Mn-Ga crystal and promote the magnetic- field- induced strain.