The influence of zirconium on Sm(CoFeCuZr)7.2 alloys for permanent magnets I: Identification of the phases by transmission electron microscopy

Permanent magnet alloys based on Sm2Co17; phase evolution in the quinary system Sm–Zr–Fe–Co–Cu

“…This R-SmCo 4 phase with c = 6.0 nm has received little attention, but its existence must be acknowledged. It is, for example, compatible with the unexplained lattice fringes having a spacing of 2.0 nm (6.0 7 3) in a high-resolution image reported by [2] for a quinary magnet alloy treated for 800 h at 850°C.…”

“…The compounds have a common sublattice, namely that of hexagonal SmCo 5 with which the strong diffraction maxima are shared. Essentially two different orientations in electron diffraction, together with high-resolution imaging, have allowed the positive identification of 1 : 3, 2 : 7, and 5 : 19, as shown convincingly in the work of [2]. There a cast magnet studied was Sm(Co 0.69 Fe 0.22 Cu 0.06 Zr 0.03 ) 7.2 (a formula given in magnetician's nomenclature which assumes that Zr replaces Co), or in at.%, 12.20 Sm, 2.63 Zr, 19.32 Fe, 60.59 Co, 5.27 Cu.…”

“…In the treatment of [28], 16 h at 800°C followed by ramping down to 400°C at 1 K/min, we assume nearequilibrium before the temperature is dropped to 400°C. The 850°C equilibrium phases of the alloy described in Section 2.1 are 2 : 17, 5 : 19, 2 : 7 and 1 : 3 [2] and, in fact, we can observe them after 16 h at 800°C. Notwithstanding the reservations about mixing Sm and Zr voiced in the previous section, it is easiest to simplify the five-component system by combining Sm and Zr to form a pseudo-quaternary system (Sm, Zr) -Fe -Co -Cu.…”

“…It should be noted here that in the treatment (3) of Sect. 2.1 the electron diffraction pattern [2] of the 2 : 17 matrix with a [1,0, -1,0] zone axis shows, in addition to reflections attributed to the 1 : 3 lamellae, some satellite reflections that were not discussed. These turn out to be just the satellite reflections from the 2 : 7 phase shown in Fig.…”

“…The alloy was processed one of three ways by annealing followed by water quenching: (1) 1050°C (9 h), (2) 850°C (800 h), and (3) 1050°C (10 h) then 850°C (40 h). The phases observed after treatments (1), (2), and (3) were: (1) R-(and possibly H-) 2 : 17 + R-2 : 7, (2) R-2 : 17 + R-2 : 7 + R-5 : 19, (3) 2 : 17 + 1 : 3 + 2 : 7 + 5 : 19, all R. The 1 : 3 phase forms the lamellae or platelets parallel to the basal plane of the 2 : 17 matrix, and the mixture of 2 : 7 + 5 : 19 is located in bands that are reminiscent of the cell boundaries in magnets.…”