Study of Co-Ni-Al Alloys with Magnetically Controlled Shape Memory Effect

Abstract

Abstract. The methods of electron microscopy, resistometry and magnetometry are used to study ten (36-38)Co − (32-36)Ni − (27-30)Al (at. %) alloys. Cast coarse-crystalline and microcrystalline alloys made by melt spinning in a helium atmosphere are considered. It is shown that the martensite start temperature M s becomes 30-50°C lower as grains are refined to 1 µ m. Replacement of 1 at. % cobalt by nickel and 1 at. % aluminum by nickel makes the temperature interval of the В2 ↔ L1 0 martensite transformation (30-60)°C and (100-110)°C higher respectively. The martensite transformation hysteresis is about 100 degrees. The melt-spun Co 38 Ni 34 Al 28 alloy with the transformation temperatures М s = 31°С, М f = -34°С, А s = -6°С, А f = 70°С and Т с = 98°С is a material possessing the magnetically controlled shape memory effect.

Electromagnetic characterization of metallic sensory alloy

“…Note that these electrical measurements of transformation temperatures are in good agreement with the magnetically measured temperatures at 310K (225K) for the austenitic (martensitic) transformations. In agreement with [3], an increase in resistance of ~ 15% -20% is measured across the austenitic -martensitic transformation, with an equivalent decrease in resistance during the reverse transformation. A strain-induced martensitic transformation would therefore be anticipated to produce an increase in the resistivity of the sample on the order of 15% -20%.…”

“…Ferromagnetic shape memory alloys undergo a martensitic transformation in response to temperature, strain, or external magnetic field [1][2][3]. While much previous work has focused on applications of the material for the development of mini-actuators [4], sensory applications of the material also have been suggested in the literature [5].…”

“…Along with changes in the magnetic properties of the FSMA, changes in the resistivity also are anticipated between the martensitic and austenitic phases [3]. To track this effect in the alloys under investigation at NASA LaRC, temperature-dependent resistivity measurements were performed.…”

Visible microactuation of a ferromagnetic shape memory alloy by focused laser beam

“…The detailed preparation of a bulk sample of similar composition was detailed previously [8]. During melt-spinning we controlled the cooling rate to ensure that we get a two-phase (β + γ ) structure in the sample [9], unlike the pure β phase structure that generally forms [10]. This was done in order to introduce some ductility of the ribbon in our case, so that it would be more elastic to work with.…”

Structure Evolution of Ni36Al27Co37 Alloy in the Process of Mechanical Alloying and Plasma Spheroidization

“…Varying the elements contents in a narrow range also allows for varying martensitic transformation temperatures in a wide range [9]. For this work, the composition Ni 36 Al 27 Co 37 is chosen according to papers [10][11][12][13], as it indicates SME at about room temperature, that can be used in a wide range of applications.…”