Phase diagram evaluation and experimental characterization of the Al-Bi-Ge ternary system

In this work, the ternary system Al-Bi-Ge has been studied. Phase diagrams were calculated using Pandat software while experimentally tested alloys come from three vertical and two isothermal sections. The three vertical sections Al-BiGe, Bi-AlGe and Ge-AlBi were investigated by differential thermal analysis (DTA) and experimental phase diagrams were compared with calculated ones based on the experimental results. Selected alloys from the isothermal section at 400 °C and as-cast samples were investigated by X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The microstructure of the investigated samples was characterized by optical microscopy (OM) and the scanning electron microscopy (SEM). The microstructure of all samples annealed at 400 °C, consists of three phases L, (Al) and (Ge), while in the microstructure of as-cast samples phases (Al), (Bi) and (Ge) are detected. Microstructure of as-cast samples were compared with calculated isothermal section at 25 °C. Brinell hardness, electrical conductivity and electrical resistivity were measured for selected ternary alloys. Based on the experimental values and using a suitable mathematical model, these properties were predicted by RSM methodology for all composition ranges.