Fe-Al系金属间化合物中的微观缺陷和电子密度

MICRODEFECTS AND ELECTRON DENSITIES IN Fe-AlINTERMETALLIC COMPOUNDS

对二元Fe-Al合金,含Cr和Si的Fe3Al合金的正电子寿命谱侧量表明:随着二元 Fe-Al合金Al含量的增加,空位浓度增加,微孔洞的开空间增大,在Al含量高于40%(原子分数)的 B2-FeAl合金中存在着较高的空位浓度和开空间相当于Fe中10-15个空位聚集体的微空洞,在B3-FeAl和D03-Fe3Al合金中,晶格中最邻近的Fe－Al原子对之间发生Fe d-Alp杂化作用,Al的3p电子与Fe的3d电子被局域化并形成共价键,导致合金中的自由电子密度降低,二元Fe-Al合金中的平均电子密度随着Al含量的增加而下降,用Cr元素对Fe3Al进行合金化,合金基体和晶界处的自由电子密度均增加;而加入Si元素,合金基体和晶界处的自由电子密度均减小,讨论了Fe-Al合金的微结构对其力学性能的影响。

Positron lifetime measurements have been performed in binary Fe-Al alloys with different compositions and Fe3Al alloys doped with Cr and Si. The experimental results show that the concentration of vacancy and the open volume of microvoid increase with increasing Al content in binary Fe-Al alloy. Higher concentration of vacancy, and microvoid with the size equivalent to 10-15 vacancies are present in B2-FeAl alloy with above 40% Al (atom fraction). In B2-FeAl and D0(3)-Fe3Al alloys, the 3d electrons of Fe atoms and 3p electrons of Al atoms are localized to form covalent bonds due to strong Fe d-Al p hybridization between nearest neighbor Fe-Al atom pairs, which decreases the density of free electron in the alloy. The mean electron density in binary Fe Al alloy decreases with the increase of Al content, For Fe3Al alloyed with Cr, the electron densities in the bulk and at grain boundary increase simultaneously; in contrast, for Fe3Al alloy doped with Si, the electron densities in the bulk and at the grain boundary decrease simultaneously. The influence of microstructure on the mechanical properties of the alloys has been discussed.