The microstructure of hypoeutectic Al-9.21wt.%Si alloy solidified under 5.5 GPa was studied. The results show that the solidification microstructure is refined. The primary a phase is the extended solid solution. The solid solubility of Si in α phase is up to 8.26wt.%. The growth mode of the α phase is cellular, and this cellular growth mechanism is interpreted in terms of the decrease of the diffusivity and the extended solid solution under high pressure. By calculation, it can be known that the the diffusivity of solute in the liquid under normal pressure is as high as two hundred times that under high pressure. The microhardness of the hypoeutectic Al-Si alloy solidified under high pressure is higher than that of solidified under normal pressure. After annealing, Si precipitates from the solid solution, the microhardness of the alloy decrease, but, still higher than that of solidified under normal pressure.
A l-9.21%S i亚共晶铝硅合金在5.5 GPa高压下凝固,获得接近单一α相的超高过饱和固溶体.对超过饱和固溶体进行时效处理,获得了弥散分布的细颗粒S i相,合金的性能有非常大的提高.分析了时效处理温度和保温时间对析出组织的影响.高压凝固获得超高过饱和固溶体后进行时效处理,有可能成为制备某些特殊材料的新方法.
