The phase diagram of the terbium-gold alloy system

The terbium-gold phase diagram has been investigated in the 0-100 at% Au fi eld by differential thermal analysis (DTA), X-ray diffractometry (XRD), opt ical microscopy (LOM), scanning electron microscopy (SEM) and electron prob e microanalysis (EPMA). Eight intermetallic phases were found, namely: Tb2A u orthorhombic oP12-Co2Si, peritectic decomposition at 1000 degrees C, TbAu , L.T. form, orthorhombic oC8-CrB type and H.T. form, cubic cP2-CsCl type, congruent melting at 1590 degrees C, Tb3Au4 trigonal hR42-Pu3Pd4 type, peri tectic decomposition at 1340 degrees C, Tb7Au10 tetragonal tI136-Gd7Au10 ty pe, peritectic decomposition at 1210 degrees C, TbAu2 tetragonal tI6-MoSi2 type, congruent melting at 1265 degrees C, TbAu3 orthorhombic oP8-TiCu3 typ e, congruent melting at 1215 degrees C, Tb14Au51 hexagonal hP65-Gd14Ag51 ty pe, peritectic decomposition at 1175 degrees C, and TbAu6 tetragonal tP56-S mAu6 type, peritectic decomposition at 855 degrees C. Four eutectic reactio ns were found to occur at 880 degrees C and 20.0 at% Au, at 1195 degrees C and 62.5 at% Au, at 1160 degrees C and 71.0 at% Au and finally at 805 degre es C and 89.0 at% Au. A catatectic reaction occurs in the Tb-rich region. T he experimental results are discussed and compared with the general behavio ur of the other R-Au systems. (C) 2000 Elsevier Science Ltd. All rights res erved.