Magnetic-Field-Induced Strains of Bonded Ni--Mn--Ga Melt-Spun Ribbons

Non-stoichiometric Ni₅₀Mn₂₇Ga₂₃ polycrystalline ribbons are prepared by melt-spinning technique. The magnetic-field-induced strain (MFIS) of Ni--Mn--Ga bulk alloy prepared by bonding the melt-spun ribbons is obtained. The experimental results show that Ni₅₀Mn₂₇Ga₂₃ bonded ribbons exhibit a typical thermal-elastic shape memory effect in the thickness direction. The martensitic transformation strain of bonded ribbons is an expansive strain of about 0.3\% without the magnetic field and a contractive strain of about -0.46% at the magnetic field of 1T. The field can not only enhance the value of the martensitic transformation strain of the bonded ribbons, but can also change the direction of the strain. The bonded ribbons alloy presents negative MFIS and obtains a larger value of the strain though influenced by the adhesive between the ribbons. Therefore, the preparation technique of the Ni--Mn--Ga bulk alloy by bonding melt-spun ribbons is helpful to get rid of the size restriction of the ribbon and to broaden the applications of the ribbons.