The Gd-Ni-Al system: Phases formation and isothermal sections at 500℃ and 800℃

摘要

Phase relations in the Gd-Ni-Al ternary system have been established for two isothermal sections (500 and 800℃) based on X-ray powder diffraction analysis (XRD), Light Optical Microscopy (L0M), Scanning Electron Microscopy (SEM) coupled with Energy dispersive Micropfobe Analysis (EPMA) on about 31 annealed alloys in the 50-100 at.% Al region. Seven intermetallic phases have been identified in samples annealed at 500℃ and 800℃: Gd_3Ni_5Al_(19) (oS108-Gd_3Ni_5Al_(19)), Gd_4Ni_6Al_(23) (mS66-Y_4Ni_6Al_(23)), GdNiAl_4 (oS24-YNiAl_4), GdNiAl_3 (oP20-YNiAl_3), Gd_3Ni_7Al_(14) (hP72-Gd_3Ni_7Al_(14)), GdNiAl_2 (oS16-CuMgAl_2) and GdNi_2Al_3 (hP18-GdNi_2Al_3). One additional ternary phase GdNi_3Al_9 (hR78-ErNi_3Al_9) has been found only in samples annealed at 800 °C. The isothermal sections have been determined and then compared, the crystal structures of the ternary phases have been confirmed and lattice parameters calculated.