添加B对高Nb-TiAl合金高温抗氧化性的影响

Effect of B addition on the high temperature oxidation resistance of high-Nb-containing TiAl alloys

研究了添加B对Ti45Al8Nb合金在900℃空气气氛下抗氧化性的影响.结果表明,B的添加对Ti45Al8Nb合金全片层组织的片层团尺寸有明显的细化效果.但B的加入对该合金高温抗氧化性的作用具有两面性.适量B的加入会抑制TiO 2的生长,促进Al 2O 3的生长,从而优化合金表面的氧化膜结构,提高合金的高温抗氧化性;同时,B的加入会减小合金表面氧化膜中的裂纹尺寸,增强氧化膜与基体的黏附性.而加入过量的B,O原子的内扩散通道增加,不利于改善合金的高温抗氧化性.

The influence of B addition on high temperature oxidation of Ti45Al8Nb alloys was investigated in air at 900℃.The results showed that the lamellar size of alloys was refined significantly due to the B addition.However,the effect of B addition on the high temperature oxidation behavior of alloys had dual character.With the proper amount of B addition,the growth of TiO 2 layer was suppressed and the growth of protective Al 2O 3 layer was improved,which markedly enhanced high temperature oxidation resistance of the alloys by optimizing the structure of oxide scale.Meanwhile,the size of crack in the oxide scale was decreased while B was added.This indicated that the adhesion between oxide scale and matrix was improved.However,excessive addition of B was detrimental to the high temperature oxidation resistance by increasing the inner diffusion channel of oxygen.