The rotary-bending fatigue tests of a high Nb-containing beta-gamma TiAl alloy based on microstructure control have been conducted at 800 °C. A fine nearly lamellar microstructure with the lamellar colony of 80 µm and slight content of B2 phase of 2% is obtained by an improved two-step heat treatment. The rotary-bending fatigue results perform the scattered S-N data, flat S-N fitting curve and an excellent fatigue limit reached at 355 MPa. SEM results exhibit an obvious transition between stable crack growth and fast fracture surface. Massive cracks initiate at lamellar interface, colony boundary and B2 phase on the specimen surface, which coalesce and propagate from the margin to the center of specimen. TEM analysis indicates that dislocation glide and mechanical twinning are the mainly deformation mechanism. The interlamellar and translamellar fracture result from dislocation pile-up and the inclined slip band or mechanical twinning, respectively.

基于微结构控制的高含Nb的β-γTiAl合金的旋转弯曲疲劳试验已在800°C下进行。通过改进的两步热处理，可以得到层状菌落为80 µm且B2相的微量含量为2％的细微的近层状显微组织。旋转弯曲疲劳结果执行了分散的SN数据，平坦的SN拟合曲线，并且在355 MPa时达到了极好的疲劳极限。SEM结果表明，在稳定的裂纹扩展和快速的断裂表面之间有明显的过渡。大量裂纹始于试样表面的层状界面，菌落边界和B2相，这些裂纹聚结并从边缘扩散到试样中心。TEM分析表明，位错滑动和机械孪生是主要的变形机理。