Ferrous Polycrystalline Shape-Memory Alloy Showing Huge Superelasticity

TLDR

Shape‑memory alloys such as Ni‑Ti and Cu‑Zn‑Al exhibit reversible strains of several percent via superelasticity, but only Ni‑Ti alloys are currently practical for applications. The authors report a ferrous polycrystalline alloy that achieves over 13 % superelastic strain and >1 GPa tensile strength—almost double the strain of Ni‑Ti—while also providing high damping and reversible magnetization, making it a promising high‑damping sensor material.

Abstract

Shape-memory alloys, such as Ni-Ti and Cu-Zn-Al, show a large reversible strain of more than several percent due to superelasticity. In particular, the Ni-Ti-based alloy, which exhibits some ductility and excellent superelastic strain, is the only superelastic material available for practical applications at present. We herein describe a ferrous polycrystalline, high-strength, shape-memory alloy exhibiting a superelastic strain of more than 13%, with a tensile strength above 1 gigapascal, which is almost twice the maximum superelastic strain obtained in the Ni-Ti alloys. Furthermore, this ferrous alloy has a very large damping capacity and exhibits a large reversible change in magnetization during loading and unloading. This ferrous shape-memory alloy has great potential as a high-damping and sensor material.