The H-induced fracture behavior in hot rolled medium Mn steels with and without d-ferrite

The objective of this research is to investigate the H-induced fracture behavior of Fe-6Mn-0.2C-3Al-0/0.6Si steels. Two hot-rolled steels are inter-critical annealed (0Si and 0.6Si), containing gamma + alpha-ferrite. Additionally, 0.6Si contains abundant 8-ferrite, exhibiting thin plate morphology. As for 0Si, H-induced cracks (HICs) nucleate at gamma(alpha')/alpha interfaces. Then HIC's propagation is not only transgranular cracking but also intergranular cracking. However, H-induced fracture behaviors of 0.6Si on various planes are different. As for RD//TD surface, HICs preferentially nucleate at boundaries and interior of delta-ferrite, thus reveal the intergranular cracking and the transgranular cracking, contributing to the rugged river pattern strips on fractograph. As for RD//ND surface, the layered coarse-grained delta-ferrite and layered fine-grained gamma + alpha-ferrite are stacked in sequence, which is like a composite material. The existence of the shear stress and dislocation pile-up at interfaces of (gamma(alpha') + alpha)/8 and gamma(alpha')/alpha results in HIC's preferential nucleation. Then, HICs preferentially pass through the structure of gamma(alpha') + alpha-ferrite.

Automated summary

This research investigates the H-induced fracture behavior of Fe-6Mn-0.2C-3Al-0/0.6Si steels. The study found that the microstructure of the steels greatly affects the formation and propagation of HICs, and different planes exhibit different H-induced fracture behaviors.