(中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用扫描电镜(SEM)、差热分析仪(DSC)和X射线衍射仪(XRD)，分析快速凝固过共晶Al-Si合金粉末显微组织和结构特征及其在不同退火温度和保温时间条件下过饱和固溶Si元素析出和Si相粗化行为。结果表明：快速凝固Al-Si合金显微组织中细小的块状初晶Si相和针状共晶Si相均匀分布在α(Al)基体中；气雾化过程获得的高过冷度导致Al基体晶格发生畸变，其在退火过程中得到一定程度的缓解。对快速凝固Al-Si合金中析出Si相粗化行为的分析发现，析出Si相随退火温度升高或保温时间延长而不断粗化；但其粗化不符合经典LSW理论(粗化指数n为3)，粗化机制接近由扩散速率较快的界面扩散控制(n接近2)。此外，退火温度仅对粗化速率常数和激活能有较大影响，而对粗化指数的作用不明显。
关键字: 铝硅合金；显微组织；快速凝固；粗化；显微硬度
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The microstructure characteristics of rapidly solidified hypereutectic Al-Si alloy were analyzed as function of annealing temperature and holding time by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). The precipitation and coarsening of supersaturated Si element were also investigated. The results indicate that the microstructure of rapidly solidified Al-Si alloy is composed of fine block-like primary and needle-like eutectic Si phase dispersed homogeneously in the α(Al) matrix. The structural distortion of the α(Al) matrix is observed owing to large solidification rate as a result of gas atomization. While, the structural distortion is released after annealing. The studies of coarsening of supersaturated Si in the matrix suggest that the precipitated Si phase coarsens with increasing annealing temperature or prolonging holding time. However, the coarsening behavior is different to the classical LSW theory. The coarsening mechanism is more likely to be controlled by interface diffusion with coarsening exponent near 2. Additionally, the annealing temperature only affects the coarsening rate constant and activation energy, but less affects the coarsening exponent.
Key words: aluminum-silicon alloy; microstructure; rapid solidification; coarsening; microhardness
