Effect Of Fe-doping On Magnetic Properties And Mechanical Properties Of Gd-based Amorphous Microfibers

Magnetocaloric effect is a phenomenon that the temperature of ferromagnetic or paramagnetic body changes with the variation of magnetic field intensity during adiabatic process.When applied to magnetic refrigeration technology,the magnetocaloric effect has the characteristics of environmental protection and no pollution.Additionally,the amorphous microfibers with unique microstructure and geometric characteristics,have special mechanical properties.Therefore,the research on the amorphous microfibers with magnetocaloric effect has important significance and application value.Herein,the Gd-based metallic microfibers were prepared by rotated dipping technique,and the structure of which before and after Fe-doping was characterized by XRD,DSC,SEM,and TEM/HRTEM.The testing of magnetic properties and mechanical properties of Gd-based metallic microfibers were conducted on MPMS magnetic measurement system and universal tensile sample machine,respectively,and the fracture reliability was analyzed by Weibull statistical methods.The experimental results show that the Gd-Al-Co-Fe-based metallic microfibers prepared by rotated dipping process are uniform and continuous,with characteristics of typically amorphous structure.The doping of small amount of Fe elements makes the microfibers possess a favorable thermal stability.The proper amount of Fe doping can effectively improve the degree of organization?of the metallic microfibers,and a certain amount of atomic cluster ordered regions appear on the amorphous matrix,which is essential for the enhancing of the magnetic and mechanical properties.The Curie temperature T_C of Gd-based amorphous microfibers tend to increase with the rising of Fe doping,and the T_Cof GdAlCoFe3 microfibers is the highest at 128.7 K?relatively increased by 15.3 K before doping?.Among the general magnetic performance indicators,the saturation magnetization M_s of GdAlCoFe2 microfibers reaches a peak at 264.04 emu/g.Furthermore,the values of magnetocaloric performance indexes of Gd-based amorphous microfibers increase firstly and then decrease with the rising of Fe-doping.During the external magnetic field H_ex=5 T,the maximum magnetic entropy change-?S_m^max,refrigeration capacity RC and relative cooling power RCP of GdAlCoFe1 microfibers are 10.33 J/kg·K,748.22 J/kg and 1006.90J/kg,respectively.From the perspective of microstructural changing,the doping of Fe element results in the formation tendency of atomic clusters and nano ordered microregion in micro-regions,the orderly orientation of atoms appears,and the magnetic anisotropy increases accordingly.In addition,the 3d electron layer of the doped Fe element in Gd-Al-Co-Fe quaternary alloy system enhances the RKKY indirectly exchange coupling interaction and changes the state of magnetic entropy,which in turn leads to an increase both in Curie temperature and magnetocaloric performance.The doping of Fe element improves the tensile strength of Gd-based amorphous microfibers,and the tensile strength of GdAlCoFe2amorphous microfibers reached a maximum of 1199 MPa?around 1.2 GPa?.While the GdAlCoFe2 metallic microfibers reach a peak of the fracture reliability,which means that the two-parameter Weibull modulus is 4.27,the three-parameter Weibull modulus is 2.10,and the fracture threshold is 581.93 MPa.The fracture morphology analysis indicated that the Gd-based metallic microfibers showed brittle fracture characteristics in macroscopically,and the fracture morphology is flat fractures or splitting,while there were obvious vein-like patterns and shear zones in the fractures.