定向凝固条件下Al-35%La过共晶合金的组织演变

Microstructural Evolution of Al-35%La Hypereutectic Alloy under Directional Solidification

在常规凝固条件下,Al-35%La过共晶合金可形成周期性双相枝晶组织,这种组织类似于带状组织,即其中枝晶的成分沿生长方向是周期性变化的。为了研究这种组织的形成条件,采用定向凝固技术研究了凝固速度对Al-35%La合金形貌特征的影响。结果表明:在不同凝固速度条件下,Al-35%La合金均形成周期性双相枝晶组织;同时发现:随着凝固速度的提高,初生相Al11La3呈现从周期性双相胞晶→周期性双相枝晶→周期性双相细胞晶的演变规律。在此基础上,讨论了这些组织形态的形成机理。

Under conventional solidification,microstructure of Al-35%La hypereutectic alloy formed a periodic two-phase dendritic structure,similar to band structure,the composition of the periodic two-phase dendrites exhibits periodical behavior along their growth direction.To study the conditions for forming this kind of structure,directional solidification technique was adopted to study the morphological transformation of Al-35%La alloy under different solidification rates.The results show that the structure of Al-35%La alloy retains the feature of periodic two-phase dendrites under different solidification rates.At the same time,with increasing solidification rate,the morphology of primary Al_（11）La_3 changes from periodic two-phase cell growth to periodic two-phase dendrites,and then to periodic two-phase thin cell growth.Additionally,the mechanism of forming a variety of morphologies was discussed.