Magnetostrictive and Shape Memory Properties of Heusler Type Co<SUB>2</SUB>NiGa Alloys

Abstract

We have researched and developed a new Heusler-type ferromagnetic shape memory alloy Co 2 NiGa, which has large magnetostriction caused by the magnetic-field-induced re-arrangement of martensite twin. The ribbon samples produced by rapid-solidification melt-spinning method show strong texture and large magnetostriction " of about 110 Â 10À6 for an applied magnetic field of 800 kAÁm À1 at room temperature. When increasing temperature, the martensite phase of Co 52:4 Ni 22 Ga 25:6 and Co 52:1 Ni 26:1 Ga 21:8 ribbons disappears at about 390 K and 330 K, respectively, where the drastic shape recovery arises. Some of the ribbons have good ductility and are not broken even after bending to an angle of 180 , indicating that the Co 2 NiGa system has a possibility of new ferromagnetic shape memory material with good ductility.

Pseudoelasticity and Cyclic Stability in Co49Ni21Ga30 Shape-Memory Alloy Single Crystals at Ambient Temperature

“…Similarly, magnetoplasticity could be a limiting factor for MSMAs, because the MSME involves the motion of twinning dislocations and magnetic field-induced transformations experience the same cyclic degradation as in the case of stress-induced phase transformations. [19] In CoNiGa alloys, dislocation slip characteristics can be modified by incorporating the disordered c phase (A1) or ordered c¢ phase (L1 2 ) in the ordered b matrix (austenite, B2), [14] and thus, appropriate heat treatment could provide a venue to minimize functional degradation. In addition, the high strength, relatively low density, and good corrosion resistance facilitate the utility of CoNiGa alloys in various applications.…”

“…[11] Moreover, these alloys are considered as magnetic shape-memory alloy (MSMA) candidates owing to their natural ferromagnetism. [12][13][14] The MSMAs are a new class of active materials that demonstrate large magnetic fieldinduced reversible strains due to a rearrangement of martensite twin variants or to field-induced reversible phase transformation, i.e., a magnetic shape-memory effect (MSME). [15][16][17] These phenomena can occur at frequencies of the order of 1 kHz, [18] and thus stable cyclic behavior is paramount for the envisaged applications of MSMAs.…”

Coexistence of Ferromagnetism and Superconductivity in Rapidly Quenched Ni2NbSn Heusler Alloy

“…One of the few disadvantages of the Heusler alloys is their complicated production process that contains high temperature (> 1100 K) processing for a long time (7-12 days [3][4][5]). Recently, rapid quenching method has been proved to be very efficient for cheap and easy production of large amount of the Heusler alloys [6].…”

Effects of Annealing on the Martensitic Transformation of Ni-Based Ferromagnetic Shape Memory Heusler Alloys and Nanoparticles

“…Concomitantly, the Curie temperature of the austenite T In addition to these well-investigated Ni-and Mn-based compounds, other FSMAs have been studied, i.e., Ni-Fe-Ga [21][22][23], Co-Ni-Al [24,25] and Co-Ni-Ga [26][27][28][29]. The Co-Ni-Ga Heusler system was intensively studied as a promising alternative to Ni-Mn-Ga alloys, especially for high-temperature shape memory device applications [30][31][32][33][34][35][36][37]. Co-Ni-Ga compounds generally exhibit a dual-phase microstructure: a parent phase (β) and a non-transformable secondary phase (γ).…”