Features of the HDDR process in R-Fe-B ferromagnetic alloys (R is a mixture of Nd, Pr, Ce, La, Dy and others)

Features of the conventional hydrogenation, disproportionation, desorption, recombination (HDDR) and solid-HDDR processes in some R-Fe-B (R is a mixture of Nd, Pr, Ce, La, Dy) ferromagnetic alloys were studied in the temperature range 20-990 deg. C and pressure range from 1x10-3 Pa to 0.1 MPa. This was carried out by means of differential thermal analysis (DTA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) methods. The hydride of the initial phase is formed by heating to 115 deg. C. The disproportionation of the alloys occurs in the temperature range from 320 to 800 deg. C. PHI-phase constitutes the base of the initial alloys. Among the disproportionation products, R-hydride, α-Fe and two borides (Fe2B and R1.1Fe4B4) were revealed. The initial phase in all the alloys is recovered after heating in vacuum to a temperature of 990 deg. C. Full hydrogen desorption occurs in two temperature ranges with the peaks at 200-320 and 630-715 deg. C