Magnetic and martensitic phase transitions in ferromagnetic Ni–Ga–Fe shape memory alloys

Abstract

Ferromagnetic shape memory alloys with a body-centered-cubic ordered structure in a Ni–Ga–Fe system have been developed. The alloys with the composition range of Ni 27 at. % Ga (20–22 at. %)Fe exhibit a thermoelastic martensitic transformation from a B2 and/or an L21 parent to a martensite phase, with a seven-layer modulated (14M) and a five-layer modulated (10M) structure, in the ferromagnetic state. The parent phase transforms from the B2 to the L21 structure at about 970 K during cooling, and the degree of the L21 order in the parent phase is increased by annealing at 773 K, resulting in the increase of both the martensite starting and the Curie temperatures. The ductility of these alloys is improved by introducing of a small amount of a γ-phase solid solution. Consequently, we can conclude that the present alloys are promising for ferromagnetic shape memory alloys.

Martensitic transitions and the nature of ferromagnetism in the austenitic and martensitic states ofNi−Mn−Snalloys

“…Therefore, in the past few years, there has been more research invested in the search for materials exhibiting the MSM effect and having more favorable mechanical properties at the same time. Over the past few years, other MSM alloys, such as Fe-Pt, 8 Fe-Pd, 9 CoNi-Al, 10 Co-Ni-Ga, 11 Fe-Ni-Ga, 12 and Ni-Mn-Al, [13][14][15][16] have been encountered.…”

Thermodynamics and Kinetics of Martensitic Transformation in Ni-Mn-based Magnetic Shape Memory Alloys

“…Since then alloys showing variant rearrangement under a magnetic field in their martensite phase have been categorized as ferromagnetic shape memory alloys (FMSMA) and this field of research has received much attention. Other FMSMAs, such as Fe-Pd [3], Fe-Pt [4], Ni-Mn-Al [5], Ni-Co-Ga [6], Ni-Co-Al [7] and NiFe-Ga [8], have successively been reported. In Ni-Mn-Ga systems, a huge MFIS of about 9.4 % has been reported in 14M [9] and about 12 % in non-modulated [10] martensites, despite the fact that the output stress is limited to several MPa [11,12].…”

Magnetocaloric effect in Ni-Fe-Ga Heusler alloys with Co and Al substitutions

“…The huge magnetic field induced strain (MFIS) exhibited by the Ni2MnGa alloy [2] justified the increased interest in FSMAs with Heusler disordered B2 austenite structure. Further developments indicated the off-stoichiometric Ni-Fe-Ga alloys as good candidates to replace the brittle Ni-Mn-Ga [3,4,5] due to improved mechanical durability when experiencing a reversible austenite-martensite transformation.…”

“…Article 3 , denoted Co2 and respectively Co2Al3, were prepared from high purity elements, by arc melting under argon protective atmosphere. Small pieces of each ingot were preserved as bulk reference and subjected to a thermal treatment in high vacuum for 25 h at 1223 K, followed by a quenching in iced water.…”