采用高纯铝和硅 (>99. 99wt% )配制Al 10 %Si二元合金 ,经三元钠盐变质 ,研究合金中共晶硅相。结果表明 ,铝硅合金共晶凝固时 ,硅相滞后于铝相结晶。进行钠盐变质处理后 ,共晶凝固时硅相滞后更加明显 ,并使之由片状转变为纤维状。钠盐变质后的共晶硅中有较多的孪晶 ,孪晶轴为 (111) Si,孪晶方向为 (2 11) Si,共晶两相的位向关系符合 [10 0 ]Al∥[110 ]Si。钠盐变质后的共晶硅以孪晶沟槽 (TPRE)长大机制进行分枝、细化和弯曲 ,从而证明孪晶沟槽长大机制是产生变质结构的重要途径 The Al 10% Si binary alloy was prepared by using high purity aluminum and silicon (> 99.99% by weight), and the ternary sodium salt was deteriorated to study the eutectic silicon phase in the alloy. The results show that the silicon phase lags behind the aluminum phase during eutectic solidification. After the sodium salt metamorphism treatment, the eutectic solidification of the silicon phase lag is more obvious, and make it from sheet to fibrous. There are more twins in the eutectic silicon after the sodium salt metamorphism, the twin axis is (111) Si and the twin direction is (2 11) Si. The orientation relationship of the eutectic phases accords with [10 0] Al∥ [110] Si. The eutectic silicon modified by sodium salt is branched, refined and bent by the growth mechanism of twinning groove (TPRE), which proves that the twin groove growth mechanism is an important way to produce metamorphic structure