Фазовая диаграмма системы Fe-Rh

К оглавлению: Другие диаграммы (Others phase diargams)


Fe-Rh (Iron-Rhodium) L.J. Swartzendruber The equilibrium phases of the Fe-Rh system are (1) the liquid, L; (2) the fcc phase, (gFe,Rh), which represents a complete range of solid solubility between approximately 1300 and 1394 C; (3) the high-temperature bcc phase, (dFe), with a solubility of up to 3 at.% Rh; (4) the low-temperature bcc phase, (aFe); (5) an ordered phase with CsCl structure, a›; and (6) a phase with an ordered CsCl structure, a›, which forms from the a› phase by a first-order ferromagnetic/ antiferromagnetic transition. The assessed phase diagram is based primarily on the work of [38Fal], [39Fal], [58Gib], and [63Shi]. As an aid to evaluating the assessed diagram, a thermodynamic model optimization procedure was used. Fe-rich Fe-Rh alloys are of the expanded g field type, and the a = g transformation exhibits considerable hysteresis and has a martensitic character. The ordered a› phase near the equiatomic composition undergoes a first-order ferromagnetic/antiferromagnetic transition, a› = a›, which is accompanied by a change in lattice parameter. Although most of the alloys studied have a transition temperature between 0 and 100 C, the work of [39Fal] shows that the transition temperature falls rapidly as the Rh content is decreased from the equiatomic range. The fcc phase can be retained at room temperature by rapid quenching from the g field for alloys between 25 and 40 at.% Rh. It was found that alloys between 40 and 60 at.% Rh could not be retained as fcc by rapid quenching, but that the ordering could be partially suppressed by rapid quenching into the a› field. The a and a› phases are ferromagnetic. In addition to the ferromagnetic/ paramagnetic transition, ordered alloys near the equiatomic composition undergo a first-order ferromagnetic/ antiferromagnetic transition. The effect of pressure on the a›/a› transition and the Curie temperatures of alloys near the equiatomic composition has been studied. The a›/a› boundaries move to higher temperatures and the Curie temperature decreases with increasing pressure. The width of the transition was found to decrease with increasing pressure, although this behavior is not certain. 38Fal: M. Fallot, Ann. Phys., 10, 291-332 (1938) in French. 39Fal: M. Fallot and R. Hocart, Rev. Sci., 8, 498-499 (1939) in French. 58Gib: W.S. Gibson and W. Hume-Rothery, J. Iron Steel Inst., 243, 243-250 ( 1958). 63Shi: G. Shirane, C.W. Chen, P.A. Flinn, and R. Nathans, Phys. Rev., 131, 183- 190 (1963). Published in Bull. Alloy Phase Diagrams, 5(5), Oct 1984. Complete evaluation contains 4 figures, 6 tables, and 35 references. 1