Precipitation kinetics of Cu-rich particles in super duplex stainless steels

Complex precipitation behavior of Cu-rich particles (CRPs) was investigated and simulated in continuously cooled quench-aged super duplex stainless steel. Atom probe tomography (APT) scanning electron microscopy showed that slow cooling resulted nonuniform multimodal CRP spinodal decomposition, while the fast conditions, more uniform CRPs with no visible decomposition found. Depletion Cu, Ni, Mn observed ferrite next to during growth, but not dissolution. Some evidence Ostwald ripening seen after cooling, condition, particle coalescence observed. Large disappeared a ferrite–austenite phase boundary when Cu depleted due diffusion austenite as also predicted by moving Dictra simulation. Comparing areas analyzed APT simulation CRP–ferrite effective coefficient early-stage about 300 times higher than at 475 °C. Using size-dependent interfacial energy equation, size distribution successfully Langer–Schwartz model implemented Thermo-Calc Prisma. Applying short aging time continuous increased hardness decreased toughness values compared solution annealed condition. A ferrite, structure, partitioning alloying elements among different phases are factors making steels complex.