Advanced Imaging of Ductile Fracture Micromechanisms

The failure of SA508 Grade 3 steel takes place by void nucleation, growth and coalescence mechanisms. The microstructural analysis found two different initiating particles, namely non-metallic inclusions and second phase particles. Our previous study revealed that these two particles show different contributions to ductile tearing mechanisms. Despite greater volume fraction of non-metallic inclusions, they surprisingly play no significant role in fracture initiation for low triaxiality cases. The study proved that ductile fracture is initiated by the coalescence of small voids nucleated from second phase carbide particles in every case. As structural materials are subjected to high triaxiality during their service life, the investigation of fracture mechanisms under high triaxiality loading is crucial. Our aim is to characterise the distinct behaviour of void initiating particles under such a high triaxiality loading similar to the service conditions of structural materials.