Precipitation kinetics of Cu-rich particles in super duplex stainless steels
Journal article, 2021

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

Precipitation kinetics

Moving phase boundary simulation

Atom probe tomography

Duplex stainless steels

Author

Vahid A. Hosseini

University West

Kjell Hurtig

University West

Daniel Gonzalez

Bodycote

James Oliver

Outokumpu Stainless Research Foundation

Nicklas Folkeson

ESAB

Mattias Thuvander

Chalmers, Physics, Microstructure Physics

Kristina Lindgren

Chalmers, Physics, Microstructure Physics

Leif Karlsson

University West

Journal of Materials Research and Technology

2238-7854 (eISSN)

Vol. 15 3951-3964

Subject Categories

Physical Chemistry

Other Materials Engineering

Metallurgy and Metallic Materials

DOI

10.1016/j.jmrt.2021.10.032

More information

Latest update

11/4/2021