Synthesis mechanism of Sm2Fe17 alloy produced in reduction-diffusion process

Abstract Sm 2 Fe 17 alloy was the precursor of Sm 2 Fe 17 N x magnetic materials. Reduction-diffusion (R/D) method was a new preparation process for the Sm 2 Fe 17 alloy, and had been widely employed as a new preparation method for rare earth-transition metal intermetallic compounds. In this text, thermodynamics and kinetics for the synthesis of the Sm 2 Fe 17 alloy by reduction-diffusion (R/D) method in the Ca-Sm 2 O 3 -Fe system were analyzed. The related synthesis mechanism of this reaction was investigated in detail by means of scanning electron microscope (SEM). The results showed that the thickness of the Sm 2 Fe 17 alloy layer versus the reaction time could be fit by the parabola law, and its growth model was determined to be: ( L 0 - L ) 2 =43.848 t , the diffusion of Sm into Fe proceeded with the formation of the Sm 2 Fe 17 phase from the very beginning of the reaction, and rich samarium phases, such as SmFe 2 and SmFe 3 , were not formed, and the rate-determining step of the R/D reaction was found to be the peritectic reaction between liquid samarium and solid iron.