The fatigue behavior of Q450NQR1 high-strength weathering steel under a loading ratio of = 0.1 was experimentally investigated in the very high cycle fatigue (VHCF) regime, elucidating the formation mechanism of the fine granular area (FGA). The results indicated that Q450NQR1 high-strength weathering steel mainly fails due to non-inclusion-induced crack initiation (NIICI) in VHCF regime. Slip in {110} and {112} plane families dominates in ferrite. Intergranular cracking results in fatigue microcracking, which in turn leads to the formation of NIICI in Q450NQR1 high-strength weathering steel. The formation of FGA was attributed to the localized severe plastic strain-induced continuous dynamic recrystallization at the tip of microcrack propagation. Moreover, it can be found that the formation of fine grains promotes the extension and aggregation of microcracks. Based on all experimental findings, a mechanism governing crack initiation in Q450NQR1 high-strength weathering steel during VHCF loading was proposed.

中文翻译：

---

Q450NQR1高强度耐候钢在极高周疲劳状态下的微观组织演变和裂纹萌生行为

在极高周疲劳（VHCF）状态下对Q450NQR1高强度耐候钢在加载比=0.1下的疲劳行为进行了实验研究，阐明了细颗粒区（FGA）的形成机制。结果表明，Q450NQR1高强度耐候钢的失效主要是由于VHCF状态下的非夹杂物诱发裂纹（NIICI）所致。铁素体中以{110}和{112}晶面族为主。晶间裂纹导致疲劳微裂纹，进而导致Q450NQR1高强度耐候钢中NIICI的形成。 FGA 的形成归因于微裂纹扩展尖端局部严重塑性应变诱导的连续动态再结晶。此外，可以发现细晶粒的形成促进了微裂纹的扩展和聚集。基于所有实验结果，提出了 Q450NQR1 高强度耐候钢在 VHCF 加载过程中裂纹萌生的机制。