PHASE-DIAGRAM AND INHOMOGENEITY OF (TBDY)-FE(T) (T=MN, CO, AL, TI) SYSTEMS

The Tb-Dy-Fe ternary phase diagram and its Tb0.3Dy0.7-Fe section in th e region of the magnetostrictive Laves phase have been investigated. D ifferent segregation behavior for Tb and Dy was proposed and experimen tally confirmed. The deviation of the TbDyFe Laves phase composition f rom its stoichiometric composition and the small Fe solubility range o f the Laves phase were also determined. Based on phase selection theor y, the pseudocongruent crystallization of REFe2 phase was confirmed. T he inhomogeneity of Tb0.3Dy0.7(FeT)(1.95) (T = Mn, Co, Al, Ti) alloys has also been investigated. Substitution of Fe by T elements always ga ve inhomogeneous as-cast alloys. The new phases Fe2Ti and RE2(FeCo) we re observed. Obvious composition variations of Tb(Dy) and Fe(Mn) were found, which could be explained as resulting from microsegregation. Ho mogeneous phases could be obtained after homogenizing annealing while the new phases and the high Tb content in the RE phase remained. The e ffects of the inhomogeneity on the alloy magnetostrictive properties w ere also discussed.