中文摘要：

研究了高强度的近片层γ-TiAl合金Ti-44Al-4Nb-4Zr-0.2Si-1B长期热暴露（700℃,10000h）前后的显微组织变化,并研究了表面缺陷对高周疲劳性能的影响。对长裂纹的疲劳起裂门槛值,引起疲劳失效的非安全尺寸的短裂纹范围进行分析,确定了该合金在热暴露下的表面缺陷的容忍限度。结果表明：热暴露能提升该合金光滑样品的疲劳强度,增加其对表面缺陷的敏感度。

英文摘要：

The changes of the microstructure of high strength near lamellar γ-TiAl alloy Ti-44Al-4Nb-4Zr-0.2Si-1B before and after thermal exposure （at 700 ℃ for 10000 h ） were investigated, and the influences of surface defects on the high cycle fatigue behaviour were studied. The fatigue crack threshold value of long cracks and the short crack range with unsafe size which could casue fatigue failure, were analyzed, and then the tolerance limitation of the surface defects of the alloy under thermal exposure was determined. The results show that the fatigue strength of the alloy smooth sample improves after thermal exposure, which can increase its sensitive to surface defects.