Ferromagnetic Co-Ni-Al Shape Memory Alloys with β+γ Two-Phase Structure

Abstract

The effects of the introduction of the (A1) phase into the (B2) phase on the mechanical and shape memory properties in ferromagnetic Co-Ni-Al shape memory alloys with the þ two-phase structure were investigated by cold-rolling, tensile tests, and bending tests. The mechanical properties were found to be improved with an increase in the volume fraction of the phase, and Co-33 at%Ni-26 at%Al alloy with V ¼ 36% exhibited excellent cold workability with a critical reduction ratio of 40%. Although the degree of shape recovery decreases with an increase in the volume fraction of the phase, it can be enhanced by training. Since two-phase þ Co-Ni-Al alloys have several advantages such as cost efficiency and workability, this alloy system is considered as being a new type of ferromagnetic shape memory alloys (FSMAs).

Martensitic and Magnetic Transformation Behaviors in Heusler-Type NiMnIn and NiCoMnIn Metamagnetic Shape Memory Alloys

“…On the other hand, all of the 7.5Co alloys have a small amount of precipitates along the grain boundaries and in the grains, as indicated by arrows in Figure 1(c), where the precipitates with the fcc structure may suppress the introduction of cracks along the grain boundaries, as reported in the Ni-Al-Fe and Co-Ni-Al alloys. [21,22] The crystal structures of the parent and martensite phases were identified with TEM observation. Figure 2 shows selected area diffraction (SAD) patterns taken from the parent and martensite phases in the Ni 45 Co 5 Mn 36.7 In 13.3 alloy.…”

Phase Equilibria and Phase Transition of the Ni–Fe–Ga Ferromagnetic Shape Memory Alloy System

“…To date, numerous alloy systems have been explored to find new FSMAs, and thermoelastic martensitic transition from the ferromagnetic parent phase has been reported in Fe-Pd, [2] Fe-Pt, [3] Ni-Mn-(Al, Sn, Sb, In), [4,5] CoNi-(Al, Ga), [6][7][8][9][10] Ni-Fe-(Al, Ga), [11,12,13] and Cu-Mn-Ga [14] alloy systems. More recently, metamagnetic SMAs have been found to exhibit thermoelastic martensitic transition from the ferromagnetic parent phase to the antiferromagnetic martensite phase in the NiCoMnIn system.…”

Influence of Co Addition on Martensitic and Magnetic Transitions in Ni-Fe-Ga β Based Shape Memory Alloys

“…1) Since then, many ferromagnetic shape memory candidates have been investigated, such as Fe-Pd, 2) Fe-Pt 3) Ni-Mn-(Al, Sn, Sb, In), 4,5) Co-Ni-(Al, Ga), [6][7][8][9][10] Ni-Fe-(Al,Ga) [11][12][13] and Cu-Mn-Ga 14) alloy systems. The present authors proposed the Ni-Fe-Ga alloy system as promising ferromagnetic shape memory materials.…”