用正电子湮没技术研究锌液对钛铝基合金的腐蚀

研究了Ti-50AI和Ti-45Al-8Nb合金在锌液中的腐蚀行为，并测量Ti-50Al和Ti-45Al-8Nb合金的正电子寿命谱，利用正电子寿命参数分别计算了合金基体和缺陷态的自由电子密度。TiAl合金自由电子密度比金属Ti和金属Al基体的低，当Ti和Al组成TiAl合金时，Ti原子和A1原子的部分价电子被局域化，TiAl合金中金属键和其价键共存。TiAl合金晶界缺陷的开空间较大，晶界缺陷处的自由电子密度较低，金属键结合力较弱。在TiAl合金中加入Nb元素，Ti-45A1-8Nb合金基体和晶界的自由电子密度增大，明显减慢了锌液对钛铝基合金的溶解速度。

Investigation on Liquid Zinc Corrosion of TiAI Alloy by Positron Annihilation

The static isothermal corrosions of Ti-50A1 and Ti-45A1-8Nb alloys in liquid zinc were studied and their positron lifetime spectrums were measured. The densities of free electrons of the bulk and microdefects in these alloys were calculated by using the positron lifetime parameters. It is found that the density of free electrons is lower in the bulk TiAl alloy than in Ti or Al matrix due to the localization and aggregation of some valence electrons in Ti and Al atoms to form TiAl alloy with a mixture bond of metallic bond and covalent bond. The large open defects occurs in the grain boundary of TiAl alloy and the bonding strength of grain boundary is weak due to the low density of free electrons. Then the densities of free electrons in the bulk and the grain boundary will simultaneously increase due to the great decrease of dissolution rate in liquid zinc as the TiAl alloy is alloyed with Nb