Structural, Physical and Damping Properties of Melt-Spun Ni-Mn-Ga Wire-Epoxy Composites

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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.