Production of Nd and Nd-Fe Alloys from NdCl₃ by Calciothermic Reduction

This study presents a metallothermic reduction mechanism for fabricating Nd and Nd-Fe alloys at 850-1050 °C using anhydrous NdCl₃ and Ca, which have relatively low melting points. Our method decreased the process temperature while improving the recovery rate of Nd using the thermodynamic parameters of the CaCl₂-KCl-NaCl and Nd-Fe liquid solutions. To reduce the activity of the product (CaCl₂), the optimal composition of the CaCl₂-KCl-NaCl molten salt was XCaCl2=0.4 (XKCl:XNaCl=6:4). The molten metal bath (Nd or Nd-Fe) that formed at the bottom of the reaction zone during Nd and Nd-Fe alloy production absorbed metal particles generated in the molten salt during the reaction, thereby facilitating ingot formation. In Nd produced at 1050 °C using 1.2× the stoichiometric amount (by mass) of Ca, the Nd recovery rate was 97.0%. Moreover, in the Nd-Fe alloys produced at 1050 °C targeting eutectic compositions, the Nd recovery rate was 96.3%. Increased Fe contents in the Nd-Fe liquid solution reduced the Nd recovery rates, and the Nd-Fe alloy (Nd recovery rate: 89.8%) was produced at 850 °C, suggesting the possibility of increasing the energy efficiency of the Nd production process. The Nd-Fe alloy produced through this proposed process could be used as a raw material in the NdFeB strip casting process.