Characterization and properties of new shape memory alloys in the NiFeAl system

Wallin, Mathias; Johansson, P.; Savage, S. J.

doi:10.1016/0921-5093(91)90075-x

Cited by 14 publications

(1 citation statement)

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“…These alloys can be fabricated at elevated temperatures but were brittle with poor ductility at room temperature [4, [12][13][14][15][16]. Although these problems have largely been overcome by the addition of iron and boron [4, [17][18][19][20][21][22], the mechanical production of a usable form of the alloys is time, labor, and cost intensive.…”

Section: Introductionmentioning

confidence: 99%

Processing and characterization of Ni-Al-Fe-B shape-memory alloy wires produced by rapid solidification

et al. 1994

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This work describes net-shape ductile wires of Ni-Al-Fe doped with boron produced directly from the melt by in-rotating-liquid (IRL) melt spinning, thus avoiding the difficult and costly problem of fabricating bulk castings. This method produces wires of 0.1 to 0.5 mm diam and lengths to 2 m. X-ray diffraction (XRD) scans showed that the as-spun wires consist of the B2, LI2, and bet martensite phases and that the B2 phase further transforms to bet martensite upon cold working. Shape-memory behavior showed an Ap temperature of ~180°C as measured by bend recovery tests and by tensile cycling tests. The effects on the wires of IRL processing parameters are discussed.the iron occupies the nickel and aluminum sites is equally, the equivalent aluminum concentration [4] 33.5%. The bulk alloy was arc melted, drop cast into 2.5 x 1.25 x 12.6 cm ingots, examined for macro-segregation, and sectioned into small pieces for melt spinning. Processing included melting in a quartz crucible by induction heating and ejecting a liquid stream into a layer of rotating liquid. The entire heating, melting, and ejection cycle occurred within 1 min to lessen any reaction between the melt and crucible. A conventional melt-spinning apparatus was altered to accept a cupped aluminum wheel for holding a liquid coolant. The coolant was held on the interior surface of the wheel by centrifugal force. The wheel velocity, ejection pressure (jet velocity), incident angle of the crucible, nozzle diameter, nozzle-tocoolant distance, temperature, and the depth of the coolant layer were variable parameters that affect the wire morphology. The crucible, ejection piping, and induction heater coil were located as far to the rear of the wheel as possible to achieve a small incident angle between crucible and coolant. The crucible was only -10 cm long and 1.0 cm diam due to the constraints of the wheel size (30 cm).The wires were examined using both optical and scanning electron microscopy (SEM). Roomtemperature XRD of both as-spun and stressed samples was made using Cu Ka radiation.The shape-memory effect was characterized by bend recovery and tensile strain recovery tests. The bend test consisted of bending the sample around a -3 mm mandrel to produce a 40° angle. The sample was heated to 300°C, and the bend angle recovery was measured as a function of temperature. A more sensitive tensile strain recovery was measured with the wire sample loaded in a tensile load frame.

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