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-fieldand 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- * Corresponding author. 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 asspun Ni-Mn-Ga wire-epoxy matrix composites and of pure epoxy.

Effect of annealing and silylation on the strength of melt-spun Ni–Mn–Ga fibres and their adhesion to epoxy

“…The untreated fibres behave in a similar way, as detailed in Ref. [10]. The silane treatment did not affect the general response of both fibre types to mechanical loading and seems not to hinder or block the stress induced twinning in the annealed fibres.…”

“…As matrix material, the epoxy system Araldite LY 3297/Aradur 3298 (with a mix ratio of 100:40 by weight) from Huntsman, USA was chosen. This standard epoxy system has Young's-modulus of about 3 GPa and a glass transition temperature at about 90 1C [10]. Dogbone shaped specimens with one fibre centred in the specimen height and width were, due to the brittleness of the fibres, produced using a two step casting process.…”

“…The properties of the as-spun and annealed fibres, 30-100 μm in width and up to 2.5 cm long, were determined and analysed in Ref. [10].…”

Superelasticity by reversible variants reorientation in a Ni–Mn–Ga microwire with bamboo grains

“…Zhang et al [18] achieved superelasticity in austenitic Ni 54.0 Mn 24.1 Ga 21.9 wires created by the Taylor method with reversible strains of up to 11.2% and plateau stress for stress-induced martensitic transformation of 115 MPa. Glock et al [19] studied the effect of annealing on the mechanical and magnetic properties of wire-spun 14M Ni-Mn-Ga wires and fabricated fiber composites from these wires. Annealing transformed the microstructure from polycrystalline to oligocrystalline (bamboo grains) and enabled twinning deformation.…”

Magnetostructural coupling and magnetocaloric effect in Ni-Mn-Ga-Cu microwires

“…For example, small size components may be used as building blocks for complex devices, precursors for composite materials, and in micro-electromechanical systems. 26,27 Their high specific surface area promises a fast, efficient heat exchange, which is beneficial for magnetic cooling. 23 In our previous works, [28][29][30] Ni-Mn-Ga microwires were fabricated by the melt-extraction technique, and the shape memory effect and superelasticity properties have been demonstrated.…”