摘要
TEM和SEM观察表明,熔态Al_(86)Mn_(14)合金急冷时形成的二十面体准晶相,存在大量精细的亚结构;准晶体因形成时的熔体冷却速率的高低,可具有“菊花”状或规则枝晶状的形态,它们都是分形结构且分形维数相近,提出了一种基于熔体中二十面体相小颗粒无规扩散和聚集过程的准晶体形成模型,据此模型进行的计算机模拟计算得到的准晶体生长图形,其形态特征与分形维数都与实验观察结果基本相符。
TEM and SEM observations prove that, icosahedral quasicrystalline formed during quenching of molten Al_(56) Mn_(14) alloys may have 'a chrysanthe mum-shaped' or regular dendritic morphology depending on the quenching rate. Both morphologies show fractal structures with similar fractal dimensions; there are substantial fine substructures in the quasicrystallites. From these results, one formation model of quasicrystalline based on the random diffusion and aggregation process of small icosahedral panicles in the melt is proposed. The results of computer simulations based on this model are in agreement with the experimental observations in both morphologies and fractal dimentions.
