Phase equilibria in the Fe-rich alloys of the ternary system NdFeSi at 500 °C

Abstract

The solid state phase equilibria and phase relationship at 500 °C in the NdFeSi ([Nd] ⩽ 40 at.% and [Si] ⩽ 40 at.%) ternary system were investigated mainly by X-ray powder diffraction, with the aid of differential thermal microanalysis and optical microanalysis techniques. The partial isothermal section at 500 °C of this system has been established. The existence of three binary compounds and two ternary compounds, namely β (NdFe2Si2) and γ (NdFeSi), was confirmed in this partial isothermal section. The β phase belongs to the tetragonal system with a = 0.4001 nm and c = 1.0061 nm. The γ phase is also a tetragonal system with a = 0.3921 nm and c = 0.6942 nm.The partial section consists of five single-phase regions, ten two-phase regions and five three-phase regions. At 500 °C, the maximum solid solubility of Si in Nd2Fe17 is 12 at.%. The γ phase has a homogeneity range, while the β phase is a non-variable compound.