The crack initiation mechanism of laser powder bed fusion (LPBF) Ti6Al4V was investigated at elevated temperature up to very high cycle fatigue (VHCF) regime. The competition concerning defect location is elaborated using the stress intensity factor range and Z-parameter model. Additionally, localized high stress near the defects is responsible for plastic strain localization in the non-prior α' region, following the grain refinement and fragmentation in the larger grains nearby, which is strongly associated with the formation of microcracks and fine granular area. Meanwhile, the process is facilitated by reducing dislocation resistance and activating multiple slip systems due to high temperature.

研究了激光粉末床熔合 (LPBF) Ti6Al4V 在高温直至超高循环疲劳 (VHCF) 状态下的裂纹萌生机制。使用应力强度因子范围和 Z 参数模型阐述了关于缺陷定位的竞争。此外，缺陷附近的局部高应力是非先验 α' 区域的塑性应变局部化的原因，紧随其后的是附近较大晶粒的晶粒细化和碎裂，这与微裂纹和细颗粒区域的形成密切相关。同时，通过降低位错阻力和由于高温激活多个滑移系统来促进该过程。