The solidification microstructures of high content Si_P/Al composite prepared by pressureless infiltration

Infiltration and solidification microstructures of high content Si_P/Al composites fabricated by pressureless infiltration were investigated in the paper. The water quench microstructure and the solidification microstructures of Si skeleton clearance were compared and analyzed particularly. The results show that the water quench microstructure of Si skeleton clearance is pseudo-eutectic microstructures which is the solidification microstructure of infiltration melt with hypereutectic component of Al-Si alloy. High velocity solidification of melt prevents Si atoms from separating out and diffusing availably. However, when the melt solidified with slow cooling velocity, the residual liquid phase of Si skeleton clearance occupies smaller proportion in whole system for Si skeleton existence. With primary Si separating out, Si skeleton turn into gradually a kind of continuous reticulate structure. The Si skeleton clearance was diminished. The residual liquid phase with hypereutectic component were separated from Si skeleton and surrounding the Si skeleton clearance. In the time, a microstructure similar to the separate-eutectic microstructure occurred in the interspaces of Si skeleton. Namely, the primary Si and the eutectic Si were separated on the surface of Si_P porous skeleton under slow cooling conditions. Solidification microstructures was a phase and there were no typical eutectic microstructures in the Al alloys phase of the composites. Furthermore, the Si phase volume fraction depends on the infiltration temperature.