微量稀土对工业纯铝中杂质相的变质行为

Modification Behavior of Trace Rare Earth on Impurity Phases in Commercial Pure Aluminum

采用SEM ,EDAX ,TEM等分析研究了稀土对工业纯铝中富Fe(Si)杂质相的变质作用及机制。结果表明 :富铈混合稀土 (RE)是一种有效的变质剂 ,可使铝中杂质相由粗大长针 (条 )状或骨骼状变为细小的团球状或短棒状 ,且分布较均匀 ,提高了材料的力学性能 (尤其是塑性 )。其变质机制主要是因稀土在固 /液界面前沿的富集 ,导致了稀土进入杂质相形成 (AlFeSiRE)的复杂化合物 ,或吸附在杂质相表面阻碍其长大。但过量稀土易导致第二相数量增多 ,降低材料塑性 ,其加入量应小于 0 .0 7% (质量分数 )

Modifying effect and mechanism of trace rare earth on Fe(Si) rich impurity phases in commercial purity Al were studied by SEM, EDAX, TEM, etc. It is found that Ce rich mixed rare earth(RE) is an effective modifying agent, which makes the coarse Fe rich impurity phases transform into complex compounds of tiny, sphere/short stick form, thus improving mechanical properties of this material. Its modifying mechanism is mainly that RE gathering at solid/liquid interface forward enters into the impurity phases, forming complex (AlFeSiRE) compounds; or is adsorbed at the impurity phases surface, impeding the growth of impurity phases; however, excessive RE will result in the increasing of RE compounds (secondary phases), reducing plasticity of this material. Therefore, its addition amount should be less than 0 07% (mass fraction).