Promising ferromagnetic Ni–Co–Al shape memory alloy system

A system of ferromagnetic β phase Ni–Co–Al alloys with an ordered B2 structure that exhibits the shape memory effect has been developed. The alloys of this system within the composition range Ni (30–45 at. %) Co–(27–32 at. %) Al, undergo a paramagnetic/ferromagnetic transition as well as a thermoelastic martensitic transformation from the β to the β′(L10) phase. The Curie and the martensitic start temperatures in the β phase can be controlled independently to fall within the range of 120–420 K. The specimens from some of the alloys undergoing martensitic transformation from ferromagnetic β phase to ferromagnetic β′ phase are accompanied by the shape memory effect. These ferromagnetic shape memory alloys hold great promise as new smart materials.