Structural, physical and damping properties of melt-spun Ni–Mn–Ga wire-epoxy composites

Abstract

Ni–Mn–Ga is a ferromagnetic shape memory alloy that exhibits large, magnetic-field- and stress-induced strains via energy dissipating twinning when processed into single crystals. Grain boundaries suppress twinning and render polycrystalline Ni–Mn–Ga brittle. Ni–Mn–Ga/polymer composites overcome the drawbacks of polycrystals and could thus provide a less expensive and easier to handle alternative to Ni–Mn–Ga single crystals for damping applications. Ni–Mn–Ga wires were produced by melt-spinning and were polycrystalline in the as-spun state. Annealed wires were ferromagnetic at room temperature with non-modulated martensite and a bamboo microstructure. The annealed wires displayed a hysteretic stress–strain behavior typical for twinning. Ni–Mn–Ga wire-epoxy matrix composites were fabricated with as-spun and annealed wires. The damping behavior of annealed Ni–Mn–Ga wire-epoxy matrix composites was higher than that of as-spun Ni–Mn–Ga wire-epoxy matrix composites and of pure epoxy.