Al-Pd-Fe合金凝固组织中复杂合金相的结构分析

Structure analysis of complex alloy phases in as-solidified microstructures of Al-Pd-Fe alloy

应用扫描电镜和透射电子显微方法分析Al75Pd15Fe10铸态合金凝固组织中复杂合金相的分布、成分以及微观结构特征。针对凝固过程中形成的两种复杂合金相,对比分析其中原子团排布的局部及长程特征,并对其形成条件进行讨论。结果表明:凝固组织中同时存在两种经历不同相变过程而形成的、但含有以同类柱状(1.6nm周期)原子团为基本结构单元的复杂合金相,它们分别属于具有高密度缺陷的十面体准晶和相关近似晶体相(ε16)。与ε16结构相比,准周期结构的形成温度区间相对较高;在Al-Pd-Fe复杂合金相结构形成的成分范围内,Pd含量的增加和凝固速度的降低有利于原子团的充分形成,也有利于原子团分布密度的增大以及长程排列周期性的建立。

The scanning electron microscopy and transmission electron microscopy were used to analyze the distributional, compositional and microstructural characteristics of the complex alloy phases（CAPs） formed in the as-cast Al75Pd15Fe10 alloy.For the two CAPs formed during the solidification, the local and long-range features determined by the arrangement of atom clusters were compared, and also the formation conditions were discussed.The results show that there exist two kinds of CAPs formed through different phase transition processes but containing same type of columnar atom clusters with 1.6 nm periodicity as the basic structural building blocks.The two CAPs belong respectively to a decagonal quasicrystal with defects of high density and defective crystalline phase（ε16）.Prior to the formation of the ε16 crystalline structure, the quasiperiodic structure forms at higher temperature.Within the compositional range suitable for the formation of an Al-Pd-Fe complex structure, increasing the Pd-content and slowing down the solidification rate will be favorable to form atom clusters with structural integrity, and also favorable to increase the distributional density and establish long-range periodicity for the arrangement of atom clusters.