Cr和Mo对Fe3Al合金中微观缺陷和电子密度的影响

测量了二元Ｆｅ３Ａｌ及含Ｃｒ或Ｍｏ的Ｆｅ３Ａｌ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。实验结果表明，Ａｌ和Ｆｅ结合形成Ｆｅ３Ａｌ合金时，Ａｌ原子提供价电子与Ｆｅ原子的３ｄ电子形成局域的共价键。Ｆｅ３Ａｌ合金中金属键和共价键共存。Ｆｅ３Ａｌ合金晶界缺陷的开空间大于Ｆｅ空位或Ａｌ空位的开空间，晶界缺陷处价电子密度比基体低，晶界的键合力较弱。在Ｆｅ３Ａｌ合金中加入Ｍｏ，降低了合金中的

Effects of Cr and Mo on microdefects and valence electron densities in Fe3Al alloys

The valence electron densities of bulk and microdefects in binary Fe3Al, and Fe3Al doped with Cr or Mo have been calculated by using the positron lifetime parameters of the alloys. The result indicates that, the 3d electrons in Fe atoms have well--localized properties and tend to form covalent bonds with the valence electrons in Al atoms, the bonding nature in Fe3Al is a mixture of metallic and covalent. The large--open--volume defects occur on grain boundary in Fe3Al and the bonding cohesion of the grain boundary is weak due to the low density of valence electron there. The addition of Mo into Fe3Al results in the decrease of the ordering energy of the alloy and the open--volume defects on grain boundary. Since the radius of Mo atom is larger than that of Fe atom, when Mo atoms substitute for Fe atoms, they will distort the lattice, enlarge the volume of the lattice and therefore decrease the density of valence electron in the bulk of the alloy. The addition of Cr into Fe3Al increases the densities of valence electrons in the bulk and the grain boundary, thusincreasing the metallic bonding cohesion. Cr is found to be a beneficial element in improving the brittleness of Fe3Al alloy.