NUCLEATING MECHANISM OF FIVE PETAL STAR-SHAPED PRIMARY SILICON
五瓣星状初晶硅形核机制

Five petal star-shaped primary silicon in hypereutectic Al-Si alloy possesses a nucleating characteristic by agglomerating from tiny polyhedron clasters with simple shape.From the veiwpoint of thermodynamics, it is a spontaneous process that the five fine tetrahedron or octahedron clasters agglomerate in a way of fivefold twinning. The agglomerated polyhedron may grow into a five petal star-shaped primary silicon. By combining clasters with smaller size than that of critical nucleation, the polyhedron can acts as a stable nucleus of primary silicon.