Experimental Investigation Phase Equilibria At 400℃ Of The Mg-Sn-Nd Ternary System

The phase equilibria of the Mg-Sn-Nd ternary at 400℃ were investigated by X-ray powder diffraction（XRD）,scanning electron microscope equipped with energy dispersive spectrometer（SEM-EDS）.Seven stable ternary compounds and one eutectoid decomposed structure（A₁）were observed in the section.The crystal structure for the phases:τ₁（Mg Sn Nd,I4/mmm,t I12）andτ₂（Mg Sn₂Nd,I-42m,t I32）were confirmed.τ₃(Mg₇₅Sn_3.5Nd_21.5)is the iso-structure of Mg₂₃Sn La₆(Zn₂₃Si Zr₆ prototype,c F120 Pearson’s code)andτ₄(Mg₄₀₊₃Sn_26.7-3Nd_33.3)has the same structure and homogeneity range of Mg_4-xSn_2+xLa₃（0.12≤x≤0.4）（Cu₄Si₂Zr₃ prototype,h P9 Pearson’s code）.The crystal structure ofτ₅(Mg₄₄Sn₃₄Nd₂₂),τ₆(Mg₄₀Sn₃₆Nd₂₄)andτ₇(Mg₁₆₊₃Sn₄₅Nd_39-3)are not determined.Two binary compounds Nd₃Sn and Nd₂Sn₃,which were not included in the Nd-Sn binary phase diagram,were detected in this work.All detected Nd-Sn binary compounds show different amounts of Mg solubility,among which Nd Sn₃ and Nd₅Sn₄ dissolve up to 10 and 6.8 at.%Mg,and the rest Nd-Sn binary phases contain 1～3 at.%Mg.The Mg Nd phase dissolves up to 6.0at.%Sn.