Investigation of aluminium-rich alloy system of aluminium-strontium-silicium

An area of the solid solution based on aluminium was studied, and the surface was plotted of the liquidus adjoining the apex of the aluminium corner of the strontium-aluminium-silicon system. The investigation was carried out by microstructure and differential thermal analyses and by the measurement of the microhardness of the component phases. A combined solubility of silicon and strontium in aluminium was studied along three radial sections at Sr-to-Si ratios of 1/2, 1/1 and 2/1. The relationships of ''composition vs. Microhardness'', obtained in these sections, made it possible to define the boundaries of the phase regions in the aluminium corner of the strontium-aluminium-silicon system at 500 deg C. The greatest solubility is that along the Al-SrAl2Si2 section at a Sr/Si ratio of 1/2. A further increase in the content of strontium brings about a drop in the solubility of silicon in solid aluminium. The projection of the liquidus surface of the strontium-aluminium-silicon system, rich in aluminium, includes four surfaces of primary crystallization: α-Al, SrAl4, SrAl2Si2 and Si. The system comprises a section of Al-SrAl2Si2 representing a quasibinary system of an eutectic type. The eutectic reaction takes place at a temperature of 640 deg C. The quasibinary Al-SrAl2Si2 section divides the aluminium corner of the Sr-Al-Si system into two independent systems Al-SrAl4-SrAl2Si2 and Al-Si-SrAl2Si2 of an eutectic type