Specific features of the interaction of alloys of the didymium-iron-boron system with hydrogen

We study the interaction of alloys of the Dd-Fe-B system M-82, M-83, M-84, and M-85 alloys with a mass content of 33–40% didymium, up to 0.5% aluminum, and 1–1.25% boron (the rest is iron)] with hydrogen using volumetric, X-ray phase, and differential thermal analysis. If the initial hydrogen pressure is 1.0 MPa, hydrides with 0.4–0.6 mass % of hydrogen are formed. The saturation of these alloys with hydrogen is accompanied by an increase in the spacing a of an elementary cell by 1.2–1.4% and in c by 0.8–1.1% (the general increase in volume is 3.2–3.9%). If the initial pressure is 0.15–0.2 MPa, the time of complete saturation with hydrogen is 15–20 min for most alloys. At 973–1033 K, the alloys under study in hydrogen disproportionate into DdHx didymium hydride (a = 0.5449 – 0.5458 nm), -iron (a = 0.2864 – 0.2866 nm), and Fe2 B iron boride (a = 0.5112 – 0.5117 nm, c = 0.4228 nm). An increase in the initial hydrogen pressure from 0.1 to 5.0 MPa is accompanied by a decrease in the disproportionation temperature to 930 K.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 2, pp. 105–112, March–April, 2004.