The Study On The Phase Diagram And Magnetic Properties Of The Fe-Pt-Nd Ternary System

The isothermal sections of the Fe-Pt-Nd phase diagram at 900℃and 500℃, the thermal stability of Nd3Pt4 compound,the polymorphic transformation of NdPt compound and the structure and magnetic properties of the Fe_60.5Pt_39.5Nd_x(x≤1.5) alloys were investigated by X-ray diffraction(XRD),differential thermal analysis (DTA), scanning electron microscopy (SEM), energy dispersion spectroscopy(EDS) and magnetic measurement techniques in this paper.The 900℃isothermal section of Fe-Pt-Nd system (Nd≤70%) consists of 13 single-phase regions (α(α-Fe),β(γ-(Fe, Pt)),γ(FePt),δ(FePt₃),ε(Pt),ζ(NdPt₅),η(NdPt₃),θ(NdPt₂),ι(Nd₃Pt₄),κ(βNdPt),λ(Nd₃Pt₂),μ(Nd₇Pt₃),ν(Fe₁₇Nd₂)), 23 two-phase regions (α+β,β+γ,γ+δ,δ+ε,ε+ζ,ζ+η,η+θ,θ+ι,ι+κ,θ+κ,κ+λ,λ+μ,μ+ν,ν+α,ν+λ,α+λ,α+κ,α+θ,β+θ,γ+θ,γ+η,γ+ζ,δ+ζ) and 11 three-phase regions (λ+μ+ν,α+ν+λ,α+κ+λ,α+θ+κ,θ+ι+κ,α+β+θ,β+γ+θ,γ+η+θ,γ+ζ+η,γ+δ+ζ,δ+ε+ζ).The 500℃isothermal section of Fe-Pt-Nd system consists of 13 single-phase regions, 23 two-phase regions and 11 three-phase regions. 13 single-phase regions:α(α-Fe),β(Fe₃Pt),γ(FePt),δ(FePt₃),ε(Pt),ζ(NdPt₅),η(NdPt₃),θ(NdPt₂),ι(β-NdPt),κ(Nd₃Pt₂),λ(Nd7Pt3),μ(Nd),ν(Fe17Nd2). 23 two-phase regions:α+β,β+γ,γ+δ,δ+ε,ε+ζ,ζ+η,η+θ,θ+ι,ι+κ,κ+λ,λ+μ,μ+ν,ν+α,ν+λ,ν+κ,α+κ,α+ι,α+θ,β+θ,γ+θ,γ+η,γ+ζ,δ+ζ. 11 three-phase regions:λ+μ+ν,λ+ν+κ,α+ν+κ,α+κ+ι,α+θ+ι,α+β+θ,β+γ+θ,γ+η+θ,γ+ζ+η,γ+δ+ζ,δ+ε+ζ.In the research of the thermal stability of Nd3Pt4 compound, it was found that the Nd3Pt4 compound with the Pu3Pd4 structure type is unstable over the temperature range of 345～860℃corresponding to the eutectoid decomposition reaction of Nd₃Pt₄→NdPt+NdPt₂ . The decomposition of Nd3Pt4 is an exothermic reaction, the heat of which is much larger than that in the composition reaction, NdPt+NdPt₂→Nd₃Pt₄, that is endothermic.At 900℃, as for Nd_42.9-xFe_xPt_57.1 and Nd_42.9Pt_57.1-xFe_x alloys, with increasing the Fe concentration, x, the Nd₃Pt₄ phase decomposes gradually into the two neighboring phasesβNdPt and NdPt₂, and nearly complete decomposition when x = 4 for Nd_42.9-xFe_xPt_57.1 and x = 3 for Nd_42.9Pt_57.1-xFe_x, respectively; and the temperature at which the eutectoid decomposition reaction of the Nd₃Pt₄ initiates was found to shift slightly to lower temperature, which means the stability of the Nd₃Pt₄ steeply falls off.By X-ray diffraction as well as differential thermal analysis and the measurements of M-T...