Phase transformation, magnetic property and microstructure of Ni–Mn–Fe–Co–Ga ferromagnetic shape memory alloys

Abstract Effects of addition of Fe and Co on the phase stability, magnetic property and microstructures were investigated for Ni–Mn–Ga. In Ni–Mn 21− x –Fe x –Ga 27 alloys, martensitic transformation temperatures decreased with increasing amount of Fe ( x ) up to 15 mol%, then slightly increased by the further addition. The crystal structure of martensite phase was 10 M for x x >15 mol%. Relatively high martensite stability was obtained for Ni 52 –Mn 16− x –Fe x –Co 5 –Ga 27 alloys. The highest stability of the ferromagnetic martensite phase was achieved in Ni 52 –Mn 6 –Fe 10 –Co 5 –Ga 27 after aging at 773 K for 3.6 ks. Martensite structure was non-modulated 2 M in this series of alloys.