Co,Cr和Ni对Fe_3Al金属间化合物相平衡的影响

EFFECT OF Co, Cr AND Ni ON PHASE EQUILIBRIUM OF Fe_3Al INTERMETALLICS

利用集团变分法,计算了 Fe-Al-Co,Fe-Al-Cr;Fe-Al-Ni三元合金700 K等温截面的 Fe3Al相区. 三个三元合金等温截面的计算结果显示,Fe-Al-Ni相图中的 Fe3Al相区最小,Fe—Al-Cr相图中的Fe3Al相区最大;根据等温截面的几何性质,可以将Co和 Ni看成是一类原子,而Cr原子属于另一类.利用 Monte Carlo方法分析了Co,Cr和Ni对Fe3Al金属间化合物原子组态的影响.从不同原子在不同亚点阵上的占位情况和原子组态图都可以看出,Cr原子倾向于占据β亚点阵;Co和 Ni原子倾向于占据α亚点阵,也有一部分Co和 Ni原子倾向于与Al原子形成B2结构晶粒,分布于DO3晶粒中,这将加剧晶体中缺陷的形成.从 Monte Carlo法得到的这些结果,也可以看出Co和Ni属于一类原子,而Cr属于另一类.

Fe3Al phase fields in the 700 K isothermal sections of Fe-Al-Co, Fe-Al-Cr and FeAl-Ni, are obtained by CVM calculation. The range of Fe3Al phase in Fe-Al-Ni isothermal section is the smallest, while that of Fe-Al-Cr is the biggest. According to the topological properties of the isothermal sections, Co and Ni can be seen as one group, and Cr belongs to another. From the results of occupation of atoms on different sub-lattices by Monte Carlo simulation, Co and Ni readily occupy alpha sub-lattice, and Cr readily occupies beta sub-lattice, which also can be seen from atomic configurations. In addition, Co and Ni atomes tend to form B2 structure grains with Al atoms, which enter the D0(3) structure granules and will increas the defects in alloys.