中文摘要：

采用反应扩散偶的方法，研究了Nb元素在a-Ti3 Al中的扩散行为.反应扩散偶经过120 h扩散退火，在高温（1 573 K）下生成了均匀的阶（ Ti , Nb）扩散层;低温（1273,1 423 K）下生成不均匀的扩散区，相组成为Ti3Al（ Nb） ,β-（Ti , Nb）及Nb2Al.采用Dayananda方法计算了体系的扩散系数，即根据一个扩散偶的浓度分布曲线计算体系的扩散系数.采用平均扩散系数来表征体系的扩散系数，得出扩散模型和相关扩散机理.结果表明：Ti和A1的主扩散系数比Nb的主扩散系数大5个数量级;Ti的主扩散系数是Al的2倍.Nb通过占据Ti的空位进行扩散，Nb的掺入阻碍了Ti元素扩散，从而提高了a-Tip A1体系的高温抗氧化性能

英文摘要：

The α2 single phase interdiffusion behavior in Ti3Al-Nb ternary system was studied at the tem- perature of 1 273 K, 1 423 K, 1 573 K, using Ti3A1/Nb single phase diffusion couples. The uniform β-（Ti, Nb） phase was formed in mid of the diffusion couple after 120 hours diffusion annealing in the high tempera- ture. On the contrary, the nonuniform diffusion layers, including Ti3Al（Nb）, β-（Ti, Nb） and Nb2Al, were formed in low temperature. The interdiffusion coefficients were calculated by the method of Dayananda, which can evaluate by the concentration dependence in one couple only. The calculation results show that the inter- diffusion coefficients of Ti and Al is five order of magnitude larger than Nb, and Nb atoms are considered to occupy Ti sites in Ti2Al, the exchanges with vacancies on Ti sublattice played a leading role in the diffusion of Ti3Al. These results can provide a theoretical basis for the mechanisms of Nb improving the oxidation resist- ance of Ti3Al.