过共晶Al-Si合金熔体中初生硅生长特性

利用等温液淬的方法,研究了Al-18%Si过共晶合金熔体中初生硅的生长行为及机制.结果表明:重熔过程中熔体中未溶解的硅相粒子,在凝固过程中可成为初生硅生长核心,并且未熔颗粒与初生硅形状之间存在明显对应关系; 初生硅的生长机制不是惟一的,既可以以孪晶凹角(TPRE)机制生长,还可以以层状机制生长,初生硅最终形状还要取决于溶质传输等动力学环境; 随着熔体过热温度的升高,凝固组织中初生硅形状由多边形向星形及树枝状转变.

Growth behavior of primary silicon in hypereutectic Al-Si alloy

The process and mechanism of primary silicon growth in the Al-Si hypereutectic melt were studied by quench interrupting. The results show that the undissolved silicon particles in the melt become the cores of primary silicon precipitated in solidification and there is a close relationship between the shape of primary silicon and undissolved silicon particles. The growth of silicon follows not only the twin plane re-entrant edge(TPRE) mechanism, but also layer mechanism as well. Meanwhile, the shape of primary silicon also relies on kinetic surroundings, such as the transmitting of solute. At higher overheating temperature, the shape of primary silicon becomes the star-shape and tree-shape.