In this work, rotating bending fatigue, scanning electron microscope in-situ fatigue, pre-fatigue (and post-fatigue) electron backscatter diffraction tests were carried out for rolled Ti–6Al–4V alloys. The macrozone sizes and orientations of the materials were classified and the effect of macrozones on fatigue cracking behavior and fracture mechanisms was studied. The results indicated that intra-granular fracture was dominated in the process of crack propagation. Basal and prismatic slip systems were favored for the macrozones whose crack paths were straight and zigzag, respectively. Multiple active slip systems can also induce the fatigue crack deflections inside grains. Moreover, fatigue crack propagation rate, threshold stress intensity factor range (ΔK_th) and fracture toughness (K_IC) were measured for different kinds of macrozones. For the macrozones favorably orientated for prismatic slip, their crack propagation resistance and ΔK_th were excellent. However, the K_IC values for different macrozones were similar. Finally, the effect of macrozone orientations on fracture mechanisms (cleavage and plastic fracture) was discussed through a combination of Schmid factor, active slip systems and the Δθ angle (between ɑ-Ti phase (0001) plane normals (c-axes) and cyclic load directions). The Δθ is an adequate parameter to predict the fatigue fracture modes.

在这项工作中，对轧制的 Ti-6Al-4V 合金进行了旋转弯曲疲劳、扫描电子显微镜原位疲劳、疲劳前（和疲劳后）电子背散射衍射试验。对材料的宏观区域尺寸和取向进行分类，研究宏观区域对疲劳开裂行为和断裂机制的影响。结果表明，裂纹扩展过程中以晶内断裂为主。裂缝路径分别为直线和锯齿形的宏观区域有利于基底和棱柱滑移系统。多个主动滑移系统也会引起晶粒内部的疲劳裂纹偏转。此外，疲劳裂纹扩展速率、阈值应力强度因子范围（Δ K _th) 和断裂韧性 ( K _IC ) 对不同种类的宏观区域进行了测量。对于有利于棱柱滑移的宏观区域，它们的裂纹扩展阻力和ΔK _th非常好。然而，不同宏观区域的K _IC值是相似的。最后，通过 Schmid 因子、主动滑移系统和Δθ角（ɑ -Ti 相（0001）平面法线（c轴）和循环载荷方向）。Δ θ是一个足够的参数来预测疲劳断裂模式。