Kinetic model for hydrogen-induced direct phase transformations in R2Fe17 (R - Sm, Y) type alloys

S.B. Rybalka1
1Bryansk State Technical University, 50-letiya Oktyabrya boulevard 7, 241035 Bryansk, Russia
At present the intermetallic compounds of R2M17 (R=Sm, Y, Dy, Ho, Gd) type have attracted much attention because of their interesting magnetic properties. In particularly, R2M17 compounds demonstrate very interesting magnetic phenomenon during their interaction with interstitial atoms (H, N, C, B). In particular, the new perspective technology well known as a HDDR-process (Hydrogenation-Decomposition-Desorption-Recombination) in R2M17 type alloys (Sm2Fe17, Sm2Co17 etc.) alloys for permanent magnets allows improve their structure and magnetic properties by hydrogen-induced reversible phase transformations. Model for evolution of the hydrogen induced direct phase transformation in R2Fe17 type hard magnetic alloys has been proposed. It is shown that evolution process of hydrogen-induced direct phase transformation in R2Fe17 type hard magnetic alloys is controlled by diffusion process of Fe atoms in low temperatures interval of 330-750oC and in high temperatures interval of 780-860oC phase transformation process is controlled by growth kinetics of rare-earth RH2 hydride phase. On the base of Kolmogorov and Lyubov kinetic theory of the phase transformations has been obtained kinetic equation that well described the isothermal kinetic diagram for this type transformation in R2Fe17 (R – Sm, Y) type hard magnetic alloys. Thus, kinetic equation obtained on the base of Kolmogorov and Lyubov kinetic theory of the phase transformations well describes the kinetics of hydrogen induced direct phase transformations in R2Fe17 alloys. Above-mentioned kinetic approach in future can be applied for others RE-Fe type hard magnetic alloys for permanent magnets (Pr-Fe, Er-Fe, Ho-Fe etc.).
Received: 27 September 2015   Accepted: 05 October 2015
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