Study On The Dy-Fe-Mn Phase Equilibrium And Structure,Properties Of Ralated Compounds

In this paper,Dy-Fe-Mn ternary series alloys and related compounds were prepared by vacuum arc melting furnace.Their structures were studied by X-ray diffraction?XRD?,the morphology and composition were investigated by scanning electron microscopy?SEM/EDS?,and magnetic properties and magnetocaloric effect?MCE?were studied by vibrating sample magnetometer?VSM?and physical property measurement system?PPMS?.The phase equilibrium and crystallographic parameters of the Dy-Fe-Mn ternary system were studied by differential thermal analysis?DTA?and Rietveld full-spectrum.The conclusions are as follows:?1?The isothermal section of Dy-Fe-Mn ternary alloy was studied and drawed at800�C.The results show that there are 5 three-phase regions,13 two-phase regions and 9single-phase regions in the isothermal section.Mn₂Dy and Fe₂Dy,Mn₂₃Dy₆ and Fe₂₃Dy₆form a continuous solid solution.The maximum solid solubilities of Mn in Fe₃Dy and Fe₁₇Dy₂ were about 3.8 at.%Mn and 21.7 at.%Mn respectively.The maximum solid solubility of Fe in Mn₁₂Dy was about 74 at.%Fe.There was no new ternary compound founded in the ternary alloy system.?2?(Mn_1-xFe_x)₂Dy?x=0.0-1.0?compounds have been studied.The results show that they are face-centered cubic crystal structures.The lattice parameter a and the unit cell volume V decrease with the increase of the x;Mn₂Dy compound exhibits antiferromagnetic properties,and the Fe₂Dy exhibits ferromagnetism.The saturation magnetization?M_S?of(Mn_1-xFe_x)₂Dy?x=0.0-1.0?compounds increase with the Fe content.Mn₂Dy compound has no magnetostrictive properties.The sample becomes more sensitive and the magnetostriction coefficient?increases with the amount of x,?can reach the maximum 350 ppm at 72 kA/m external field when x=0.9.?3?The crystal structures,magnetocaloric and hydrogen storage properties of(Fe_1-xMn_x)₁₇Dy₂?x=0-0.3?series compounds were studied.The results show that Fe₁₇Dy₂compound always maintains the structure of Th₂Ni₁₇ with the addition amount of x=0.0-0.2.The lattice parameter a and the volume V of the unit cell increase with the increase of x.The maximum magnetic entropy of the Fe₁₇Dy₂ compound was changed to3.9 J�kg^-1�K^-1.The magnetic entropy decrease with increase of Mn content.The hydrogen storage capacity of Fe₁₇Dy₂ compound at different temperatures shows that the hydrogen storage capacity is about 0.14 wt.%at 300�C,and the hydrogen storage capacity is about 0.18 wt.%when the temperature is 100�C.The structure of Fe₁₇Dy₂Co_x?x=0.0-0.15?compounds did not changewith addition of Co content,and hydrogen storage capacity did not increase with the addition of Co.?4?The structure,magnetic properties and hydrogen storage properties of(Mn_1-x-x Fe_x)₂₃Dy₆ series compounds were studied.The results show that(Mn_1-xFe_x)₂₃Dy₆series compounds always maintain the crystal structure of Th₆Mn₂₃ with the increase of Fe content,and the space group isF 3mm.(Mn_1-xFe_x)₂₃Dy₆ series compounds change obviously from ferromagnetic to antiferromagnetic to ferromagnetic.The Curie temperature?T_C?decreased and then increased with the increase of Fe content,indicating that Fe can effectively tune the T_C from 116 K to 536 K.The PCT of(Mn_1-xFe_x23)Dy₆series compounds showed that the hydrogen storage increased gradually with the Fe content.The hydrogen storage amounts at x=0.0,0.1 and 0.3 were 0.12,0.13,and 0.16wt.%,respectively.