采用XRD, SEM及TEM分析研究间隙原子C作用下Ti-46Al-8Nb-xC (x=0, 0.7, 1.4, 2.5, 原子分数, %)合金中析出相的形成规律、析出相与基体相的位向关系及其在热处理过程中的演变规律. 结果表明, 在C含量为1.4%和2.5%的合金中有长条状Ti₂AlC析出, 该析出相在铸锭制备的过程中形成, 在时效热处理中尺寸、数量和分布均无明显变化, 表现出较好的稳定性. 不同C含量合金经固溶处理和时效后析出细小针状的Ti₃AlC, 该析出相从γ相中析出, 并与γ相存在位向关系: {100}_Ti3AlC //{100}_γ, <001> _Ti3AlC//<001>_γ, 延长时效时间, Ti₃AlC尺寸略有增大, 数量变化不明显; 升高时效温度, Ti₃AlC的尺寸和数量均有显著增加.

As promising light-weight high-temperature materials, g-TiAl base alloys are considered as prospective candidates for automobile and aerospace application due to their high specific yield strength. Adding Nb to TiAl alloys increases the liquidus temperature and results in improvents of creep resistance, high temperature strength and oxidation resistance. High Nb-containing TiAl alloys have attracted much attention during past decades. With the addition of carbon in Ti-46Al-8Nb-xC alloys (x=0, 0.7, 1.4, 2.5, atomic fraction, %), the formation of precipitates, the orientation relationship between precipitates and the TiAl matrix and the evolution of the precipitates during heat treatments have been investigated in this work by XRD, SEM and TEM. The results show that lath-shaped precipitates of Ti₂AlC can be formed during the preparation of ingots with the addition of 1.4% and 2.5% of C. With good thermal stability, the size, amount and distribution of Ti₂AlC precipitates remain almost stable during the aging process. Needle-shaped precipitates of Ti₃AlC are formed in the aged alloys with 0.7%, 1.4% and 2.5% of C. And the precipitates are preferentially formed in g grains. The orientation relationship between Ti₃AlC precipitates and g phase is found to be {100}_Ti3AlC //{100}_γ and <001> _Ti3AlC //<001>_γ. Meanwhile, the precipitation behavior and morphology of Ti₃AlC are also discussed. Ti₃AlC precipitates grow slightly after prolonged aging, while the amount of the precipitates remains small. With a higher aging temperature, the size of Ti₃AlC precipitates increases significantly and an increasing amount of the precipitates is observed.