Understanding initiation processes of stress corrosion cracking by means of real time imaging and development of anti-SCC materials

开发了一种可视化方法，可以在宽窗口内实时观察应力腐蚀开裂起始过程中发生的局部和瞬态阳极事件。发现起始过程是间歇性的和非常小的阳极事件及其再钝化。裂纹往往发生在几个阳极事件相互靠近的位置。在大多数情况下，含有Si、Mg或Al的氧化物包裹体提供起始位点。应力腐蚀裂纹到达晶界处（尤其是三相点处）的δ-铁素体时，裂纹发生延迟。通过将δ-铁素体定位在晶界上，可以有效地提高钢的SCC起始寿命，最多可达体积分数的几个百分点。

A visualization method has been developed, where local and transient anodic events occurring in initiation processes of stress corrosion cracking can be observed in a wide window and in real time. The initiation process was found to be intermittent and very small-scale anodic events and their repassivation. Cracks tend to initiate at the location where a few anodic events occur in proximity to each other. In most cases, oxide inclusions containing Si, Mg, or Al, provided initiation sites. Stress corrosion cracks tend to retard when they reach δ-ferrite located on grain boundaries (especially on triple points). We may be able to effectively improve SCC initiation life of steels by locatingδ-ferrite on grain boundaries as much as up to a few % of volume fraction.