Shape Memory and Huge Superelasticity in Ni–Mn–Ga Glass-Coated Fibers

Abstract

Ni-Mn-Ga polycrystalline alloy fibers with diameters of 33 µm are reported to exhibit significantly improved ductility and huge superelastic and shape memory strains in comparison to conventional brittle bulk polycrystalline alloys. Particularly, the recoverable strain of the Ni54.9-Mn23.5-Ga21.6 fiber can be as high as 10% at 40 • C. Such optimized behavior has been achieved by a suitable fabrication process via a glass-coating melt spinning method. The superelastic properties at different temperatures and the shape memory effect of Ni54.9-Mn23.5-Ga21.6 fibers were investigated.

Effect of cobalt addition on thermal cycling behaviour of Ti50Ni(50−x)cox shape memory alloys

“…Commercially, NiTi-based alloys are considered to be one of the most successful among SMAs and are therefore used in many engineering (actuators, robotic arm grippers and pipe couplings) and medical (stents and orthodontic archwires) applications because of their appreciable mechanical properties and superior biocompatibility, respectively [5][6][7]. Moreover, the shape memory properties, i.e., transition temperatures, recovery strain and thermal hysteresis, of the binary SMAs are modified/tailored by adding ternary or quaternary elements to them [1,8,9]. During substitution for Ni and Ti in the ordered parent B2/B19' crystal structure, local atomic bonds expand or contract depending on the intrinsic properties of the ternary/ quaternary element, including crystal structure, atomic radius, electronegativity, and valency [10].…”

Dependence of Magnetic Properties of As-Prepared Nanocrystalline Ni2MnGa Glass-Coated Microwires on the Geometrical Aspect Ratio

“…Previous studies successfully utilized rapid quenching methods to fabricate Heusler-type magnetic wires [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. Notably thicker (226-µm diameter) glass-coated NiMnGa wires exhibited reversible super elasticity up to 4% tensile strain [ 40 ].…”

“…Moreover, quite thick glass coatings are reported to affect mechanical properties and deteriorate the heat exchange rate [ 32 , 41 , 42 ]. While suitable for Heusler alloys with moderate Magnetocaloric Effect (MCE) and near-ambient Curie temperatures, the glass-coated technique often failed to exhibit martensitic transformation (MT) in Heusler microwires [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. High internal stresses (100–1000 MPa), small grain size, and structural disorder associated with melt quenching are likely responsible [ 30 , 38 ].…”