Revisiting the martensite/ferrite interface damage initiation mechanism: The key role of substructure boundary sliding

Martensite/ferrite (M/F) interface damage plays a critical role in controlling failure of dual-phase (DP) steels and is commonly understood to originate from the large phase contrast between martensite ferrite. This however conflicts with few, recent observations, showing that considerable M/F initiation often accompanied by apparent island plasticity weak strain partitioning. In fact, has complex hierarchical structure which induces strongly heterogeneous orientation-dependent plastic response. Depending on local stress state, (lath) presumed be hard deform based common understanding. However, when favourably oriented, substructure boundary sliding can triggered at resolved shear comparable Moreover, careful measurements indicate occurrence sharp wedges protruding into ferrite clear steps correspondence lath boundaries, constituting jagged interfacial morphology may have effect behaviour. By taking account features, are usually overlooked literature, this contribution re-examines mechanism. A systematic study performed, accounts for different loading conditions, contrasts, residual stresses/strains resulting preceding martensitic transformation, as well possible morphologies. Crystal simulations conducted include inter-lath retained austenite (RA) films enabling sliding. The results show sliding, most favourable deformation mode martensite, trigger hence control behaviour DP steels. present finding change way mechanism