钛金属应力腐蚀机理电子理论研究

为从理论上揭示钛金属应力腐蚀行为的本质，建立了α钛晶粒及位错塞积形成的微裂纹原子 集团模型，利用递归法(recursion)计算了裂纹及晶粒内的电子结构参量(费米能级、结构能 、表面能、团簇能、环境敏感镶嵌能). 计算结果表明：氢在裂纹处的环境敏感镶嵌能较低 ，易于偏聚在裂纹处，且氢在钛金属裂纹处团簇能为正值不能形成团簇，具有有序化倾向， 趋于形成氢化物. 氢在裂纹处偏聚降低裂纹的表面能，使裂纹容易扩展. 裂纹尖端处费米能 级高于裂纹其他区域，使电子从裂纹尖端流向裂纹其他区域造成电位差，在电解质作用下裂 关键词： 递归法 电子结构 钛 应力腐蚀

Electronic theoretical study of stress corrosion mechanism of Ti metal

In order to reveal the nature of the stress corrosion of Ti theoretically, the a tomic cluster model of α-Ti and the crack formed by dislocation accumulation wa s set up. The electronic structure parameters (Fermi energy level, structure ene rgy, surface energy, cluster energy and environment-sensitive embedding energy) of α-Ti and the crack were calculated by using the recursion method. The calcul ated results show that the environment-sensitive embedding energy of H atoms in the region of crack is smaller than that in the perfect area of α-Ti, so H atom s are apt to segregate at the crack. The positive cluster energy of H atoms in t he region of the crack in Ti metal shows that H atoms can not form cluster and h ave the tendency of forming ordered phases (hydrides). When H atoms accumulate o n the surface of the crack, they reduce the surface energy of the crack, making the crack propagation easier. The Fermi energy of the tip of crack is higher th an that in other areas, so electrons move to the perfect region of α-Ti from th e tip of crack, leading to the formation of the potential difference between the crack tip and the perfect region of α-Ti, then the dissolution-corrosion proce ss of crack tip as anode occurs under the action of the electrolyte.