Solidification Of Al-Ge Alloy Under High Pressure

In this thesis, based on deeply understanding of current investigation of high pressure material science on the world, the samples of Al-Ge alloys have been prepared under high pressure. And then the solidified microstructures of the samples have been observed. The aim is to research the effects of high pressure on the phase constitution and microstructure of the alloys solidified under different pressure. First, the Al-Ge alloys, which are the content (wt.%) of Ge is 30%, 53%, 60%, and 70% respectively, were prepared by multifunctional argon-protected alloy melting furnace. Then the Al-Ge alloy solidified under superhigh pressure (4.0 GPa,5.0 GPa and 6.0 GPa) were obtained by Cubic High Pressure Apparatus (CS-1B). By observing the microstructure of the alloy, the effect of pressure were analysed. The phase constitution of the Al-60 wt%Ge alloy solidified under high pressure were characterized by X-ray diffraction(XRD). The optical microscope, SEM and TEM were used for the observation of the alloy morphology solidified under high pressure. The result of XRD shows that there is found the no new phase exists in the alloys under high pressure, compared with the microstructure solidified under normal pressure. The eutectic microstructure of Al-Ge alloys solidified under normal pressure is presented as coarse arborization like fishbone. The microstructures of prime β phases in the hypereutectic alloys change with increasing the germanium content. A amount of primary α(Al) phase is observed in the Al-60 wt.%Ge alloy solidified under high pressure, which suggests that eutectic point moving to the Ge direction with an increase of pressure in Al-Ge alloy phase diagram. So the hypereutectic microstructure of Al-Ge alloy under normal pressure transfers to hypoeutectic microstructure when it solidifies under high pressure. The fishbone microstructures of eutectic solidified under high pressure are disappeared. Under high pressure, the growth mechanism of Ge are changed under the effect of pressure and it tends to be non-faceted growth way.