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(a) Schematic of the preparation method for the Fe/NiTi composite wire and a coil of the composite wire. (b),(c) Backscattered scanning electron morphology images of the cross-section and longitudinal-section of the composite wire. (d) One-dimensional high-energy X-ray diffraction (HE-XRD) pattern of the composite wire. The inset is its corresponding two-dimensional HE-XRD pattern.
(a) The strain-controlled multi-step cyclic tensile curves (strains: 0.5%, 1.1%, 1.9%, 2.8%, 4.8%, 6.7%, and 8%) of the Fe/NiTi composite wire obtained at room temperature. (b) Enlargement of the first four tensile cycles in Fig. 2(a). (c) Plots of strain recovery ratio versus tensile strain of the composite wire and the pure Fe wire.
(a) The tensile cyclic stress-strain curves of the Fe/NiTi composite wire obtained during in situ synchrotron X-ray diffraction measurements. (b),(c) The evolutions of the d-spacing strains for Fe (110) and B2-NiTi (110) planes perpendicular to the loading direction with applied strain for a fixed a position of specimen. (d) Plot of the d-spacing of B19′-NiTi (001) plane perpendicular to the loading direction versus applied stain for a fixed a position of specimen. It is difficult to define the d-spacing of B19′-NiTi (001) plane without stress; thus, we plot the d-spacing of B19′-NiTi (001) plane versus applied stain rather than the d-spacing strain of B19′-NiTi (001) plane versus applied stain.
(a) The tensile stress-strain curve (red curve) of the Fe/NiTi composite wire after a pre-treatment of a tensile strain cycle of 8%; the tensile stress-strain curve (blue curve) of a commercial NiTi SMA wire (Ti50.8Ni49.2, at. %) obtained at room temperature. (b) The dissipated energy per unit volume by one superelastic cycle as a function of applied tensile strain for the Fe/NiTi composite and the commercial NiTi SMA wire.
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