Promising ferromagnetic Ni–Co–Al shape memory alloy system

TLDR

Ni–Co–Al alloys in the 30–45 at.% Ni, 27–32 at.% Co, and 27–32 at.% Al range exhibit paramagnetic/ferromagnetic transitions and a thermoelastic martensitic transformation from β to β′(L10). The authors developed ferromagnetic β‑phase Ni–Co–Al alloys with an ordered B2 structure that show a shape‑memory effect, with independently tunable Curie and martensitic start temperatures between 120–420 K, and demonstrate that certain compositions transform from ferromagnetic β to ferromagnetic β′ while retaining shape memory, indicating strong potential as smart materials.

Abstract

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.