Enhanced ductility and toughness by tailoring heterogenous microstructure in an ultra-heavy gauge high strength steel with severe centerline segregation

•New approach was offered to greatly enhance ductility and toughness with severe centerline segregation.•Heterogeneous microstructure was homogenized to fine multi-phase microstructure.•Centerline segregation produced more stable retained austenite.•Partitioning during annealing made local fluctuation of Mn concentration.•Similar local fluctuations of Mn concentration led to chemical homogeneity on the whole.