中文摘要：

分别在900和1000℃下对全片层Ti－45Al－8.5Nb（W, B, Y）合金进行了长期热循环（500和1000 cyc）实验,通过光学显微镜（OM）、扫描电镜（SEM）及透射电镜（TEM）研究了该合金在不同温度长时热循环条件下的显微组织稳定性.研究表明, 合金经全片层热处理工艺后凝固偏析（Al偏析）仍未完全消除,900℃下长期热循环后Al偏析处易产生不连续粗化, 合金1000 cyc热循环后仍未发现α2相的球化;1000℃下合金长期热循环后Al偏析处易析出大块γ晶粒,合金经500 cyc热循环后沿晶界产生了许多细小的等轴γ晶粒,同时α2相在γ晶粒内球化析出. 1000 cyc热循环后晶界、晶内均有大量的等轴γ晶粒析出, 且晶粒内部有不同取向的长条状或颗粒状α2相析出;合金1000℃下长期热循环后, 长条状或颗粒状α2相从γ晶粒内沿晶面{111}γ析出, α2相与γ基体保持共格位向关系.

英文摘要：

Microstructure stability in the fully lamellar Ti-45Al-8.5Nb（W, B, Y） alloy were investigated by OM, SEM and TEM after long-term thermal cycling （500 and 1000 cyc） at 900 and 1000℃. The results showed that Al-segregation could not be eliminated completely after the heat treatment. After long-term thermal cycling at 900℃, the discontinuous coarsening was inclined to occur in the Al-segregation region in the alloy. And almost no spheroidized precipitates ofα2 were observed even after 1000 thermal cycles. After long-term thermal cycling at 1000℃, the massive γ grains were generated in the Al-segregation region. After 500 thermal cycles, the spherodized α2 precipitates were produced within γ grains which were found at colony boundaries. After 1000 thermal cycles, however, the large equiaxed γ grains containing different orientation of plate-shaped precipitates of theα2 phase were observed within the lamellar structure or at colony boundaries. After long-term thermal cycling at 1000℃, the plate-shaped or particle-shapedα2, which is coherent with the γ matrix, precipitates on the {111}γ plane in the γ grain interior.