Mechanical and magnetocaloric properties of Gd-based amorphous microwires fabricated by melt-extraction

We report a systematic study of a new class of melt-extracted Gd53Al24CO20Zr3 amorphous microwires in terms of fabrication, structural characterization and evaluation of mechanical and magnetic properties. The tensile properties of the wires are characterized by a precision video gauge method and analyzed using the Weibull and lognormal methods. The three-parameter Weibull model and lognormal model based on the median rank value show consistent results and prove to be superior to the two-parameter Weibull model for the studied microwire with a smaller variation. The statistical mean tensile strength and fracture strain are calculated to be similar to 1200 MPa and similar to 2.0%, respectively, which are comparable with those of other metallic glasses. Remarkably, the microwires exhibit a large and reversible magnetocaloric effect (MCE), with the isothermal magnetic entropy change (-Delta S-m) and refrigerant capacity (RC) reaching the large values of 5.32 J kg(-1) K-1 and 467 J kg(-1) for a field change of 3 T. Albeit with a low Curie temperature, these values are superior to those reported for pure Gd and other Gd-based bulk or ribbon-shaped glasses. The mean field model-based and Langevin function analyses reveal that the second-order magnetic transition behavior of the studied wire originates from the local anisotropy associated with the fine size of the wire and derogation and fluctuation of the exchange integral. These results demonstrate the adaptability and overall excellence of the newly developed Gd-based microwires, making them multifunctional elements for MCE-based cooling applications, especially for liquid nitrogen liquefaction. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.