ThMn_(12)型金属间化合物YFe_(10-x)Si_x有序化行为的热力学研究

Ordering Behavior of ThMn_(12)-type Intermetallics YFe_(10-x)Si_x by Using Thermodynamic Model

采用四亚晶格热力学模型,辅助以第一性原理总能计算,研究了具有ThMn12原型结构的YFe10-xSix金属间化合物中元素的占位有序化行为。结果表明,YFe10.2Si1.8和YFe10Si2化合物中稀土元素Y占据2a亚晶格,Fe占据全部8i亚晶格和部分8j,8f亚晶格,Si占据部分8j,8f亚晶格,且Si更倾向于占据8f亚晶格。随温度的变化,YFe10-xSix化合物中各元素的占位有序化行为并不发生改变。本文预测结果与近期文献报道的实验结果相当吻合,间接证明了成分为YFe10Si2的化合物以ThMn12型结构的YFe10.2Si1.8相和α-(Fe,Si)固溶体相的共存形式更为合理。

Based on the fundamental thermodynamic principles,the ordering behavior of the ThMn12-type intermetallics YFe10-xSix were studied by using a general four-sublattice model supported with first-principles total-energy calculations.The results of YFe10.2Si1.8 and YFe10Si2 showed that the 2a sublattices were fully occupied by rare earth elements Y,and 8i sublattices were also fully occupied by Fe atoms,while 8f and 8j sublattices were shared by Fe and Si atoms.Meanwhile,the Si atoms prefered to occupy 8f sublattices.The site occupying fractions of all atoms in the YFe10-xSix intermetallics were not affected by the heat treatment（aging） temperature.The predicted results agreed well with the recent experimental results.And we clarified that the YFe10Si2 alloy consisted of the YFe10.2Si1.8 phase with ThMn12-type structure and α-（Fe,Si） solid solution phase rather than single YFe10Si2 phase with ThMn12-type structure.