Al含量对Fe-Al合金中微观缺陷和价电子密度的影响

Effect of Al Content on Microdefects and Valence Electron Densities in Fe-Al Alloys

关键词:  Fe-Al合金  Al含量  微观缺陷  价电子密度

Key words:  Fe-Al alloys  Al content  microdefects  density of valence electrons

摘要:

测量Fe-28Al和Fe-40Al合金的正电子寿命谱参数,计算合金基体和缺陷处的价电子密度。Fe-28Al和Fe-40Al合金基体的价电子密度(n_b)分别为4.10×10^-2a.u.和2.36×10^-2a.u.,表明当Al和Fe结合形成Fe-28Al或Fe-40Al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,Fe-28Al和Fe-40Al合金中金属键和共价键共存。两种合金均有开空间大的缺陷,晶界缺陷处价电子密度(n_b)[13.2×10^-3a.u.(Fe-28Al),4.70×10^-3a.u.(Fe-40Al)]比基体的低,表明晶界处的键合力较弱。Fe-40Al合金晶界缺陷的开空间比Fe-28Al的大。

Abstract:

Positron lifetime measurements have been performed in binary Fe-28Al and Fe-40Al alloys. The valence electron densities of bulk and microdefects in all tested samples have been calculated by using the positron lifetime parameters. The densities of valence electron in the bulks of Fe-28Al and Fe-40Al alloys are 4.10×10^-2 a.u., 2.36×10^-2 a.u. respectively. It indicates that, in Fe atom the 3d electrons have well localized properties and tend to form covalent bonds with Al atoms. The bonding nature in Fe-28Al or Fe-40Al is a mixture of metallic and covalent. The large open volume defects occur on grain boundaries in Fe-28Al and Fe-40Al alloys. The bonding cohesion of the grain boundaries in the tested samples is weak due to the low density (n_d)[13.2×10^-3 a.u. (Fe-28Al),4.70×10^-3 a.u. (Fe-40Al)] of valence electron there. The open-volume of defects on the grain boudary in Fe-40Al alloy is larger than that in Fe-28Al alloy.