Production of Nd and Nd-Fe Alloys from NdCl by Calciothermic Reduction.

This study presents a metallothermic reduction mechanism for fabricating Nd and Nd-Fe alloys at 850-1050 °C using anhydrous NdCl 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 CaCl-KCl-NaCl and Nd-Fe liquid solutions. To reduce the activity of the product (CaCl), the optimal composition of the CaCl-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.