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通过测量二元Fe3 Al以及含Si或Nb的Fe3 Al合金的正电子寿命谱参数 ,计算了合金基体和缺陷处的价电子密度 .结果表明 ,Fe3 Al合金基体的价电子密度较低 ,当Al和Fe结合成Fe3 Al时 ,Al原子提供价电子与Fe原子的 3d电子形成局域的共价键 .Fe3 Al合金中金属键和共价键共存 .Fe3 Al合金晶界缺陷处价电子密度很低 ,键合力较弱 .在Fe3 Al合金中加入Si,合金基体和晶界处的价电子密度均降低 ,晶内和晶界处的金属键结合力都减弱 .Si的加入使合金变得更脆 .在Fe3 Al合金中加入Nb降低了合金中的有序度 ,使晶界缺陷处价电子密度升高 ,金属键结合力增强 .但由于Nb的原子半径比Fe大 ,它取代Fe后晶格发生畸变 ,体积增大 ,导致合金基体的价电子密度降低 ,基体的金属键结合力减弱 .
The valence electron density of the matrix and the defects were calculated by measuring the positron lifetime parameters of binary Fe3Al and Fe3Al alloys containing Si or Nb. The results showed that the valence electron density of Fe3Al alloy matrix was low, When Fe and Al are combined into Fe3Al, the Al atom provides a covalent bond with the 3d electrons of the valence electron and the Fe atom, and the coexistence of the metal bond and the covalent bond in the Fe3Al alloy. The valence electron density at the grain boundary defect in the Fe3Al alloy is very high Low, the bonding force is weaker.After adding Si to Fe3Al alloy, the valence electron density of the matrix and the grain boundary are reduced, and the bond strength of the metal bonds in the grain boundaries and in the grain boundaries are weakened.The addition of Si makes the alloy more Brittle.Adding Nb to Fe3Al alloy decreases the degree of ordering in the alloy, which leads to the increase of the valence electron density at the grain boundary defects and the increase of the bond strength of the metal.But because Nb has a larger atomic radius than Fe, Lattice distortion occurs, the volume increases, resulting in lower alloy valence electron density, matrix bond strength weakened.