Microstructure developments of eutectic silicon particles, silicon precipitates and interfaces between eutectic silicon particles and Al matrix in an Al-6. 86wt. % Si alloy during heat treatment were studied by means of X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. Eutectic silicon particles of branch-like morphology became spheroidized and coarsened to some extent with the extending of solution treatment time. A certain amount of Si atoms dissolved in the Al matrix would aggregate, nucleate and grow into silicon precipitates in the matrix and at grain boundaries as well during artificial aging. Silicon precipitates in the matrix lied on the ｛111｝ planes of the Al matrix. Silicon precipitates on the eutectic silicon particles grew larger with aging time. A large number of twins and other crystal defects were presented in the nano-sized silicon precipitates on the eutectic silicon particles. In addition to ordinary Si∑3(111) twins, some multiple twins such as five-fold twins were also observed.%本文利用扫描电子显微镜(SEM)和高分辨透射电子显微镜(HRTEM)研究了固溶处理和时效处理过程中铝硅二元合金中硅颗粒、析出相及硅颗粒与铝基体界面处的微观结构变化特征.研究结果表明:随着固溶时间的延长,硅颗粒的形态由树枝状逐渐变成椭球状和球状；时效过程中,溶入α-Al基体中的硅原子会在铝基体中聚集,形核并形成沿铝基体{111}面生长的硅析出相,同时还会在硅颗粒上析出一层硅的纳米孪晶,这些纳米孪晶会随着时效时间的延长不断长大.硅的孪晶壳层中存在大量孪晶和其他缺陷,除了常见的SiΣ3(111)孪晶外,观察到的孪晶类型还包括多重孪晶,如五重孪晶.
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