Evolution of the role of molybdenum in duplex stainless steels during thermal aging: From enhancing spinodal decomposition to forming heterogeneous precipitates

JOURNAL OF NUCLEAR MATERIALS

卷:557

Article

Lach, Timothy G.¹  Collins, David A.¹  Byun, Thak Sang¹ 

[1] Oak Ridge Natl Lab, Mat Sci & Technol Div, 1 Bethel Valley Rd, Oak Ridge, TN 37830 USA

关键词: Duplex stainless steel;    Thermal aging;    Precipitation;    Spinodal decomposition;    Atom probe tomography (APT);    Fracture toughness;   

DOI  :  10.1016/j.jnucmat.2021.153268

来源: Elsevier

【 摘 要 】

Thermal aging of ferrite in duplex stainless steels leads to a complex microstructural evolution that can give way to large deleterious changes in mechanical properties. The microstructural evolution mecha-nisms that happen concurrently are strongly linked to minor changes in composition. By characterizing duplex stainless steels with various compositions over a range of aging conditions, it was revealed that adding a modest amount of Mo to cast austenitic stainless steel (such as changing from grade CF3 to grade CF3M) not only increases the kinetics of spinodal decomposition and Ni-Si-Mn-rich G-phase pre-cipitation, but it also forms a separate Mo-rich phase. At shorter equivalent aging times, Mo segregates from Fe and towards Cr accelerating spinodal decomposition. At longer aging times, Mo enriches in the Ni-Si-Mn clusters before phase separating into an adjoined Mo-rich cluster. These phase changes and pre-cipitation events result in a rather steep drop in fracture and impact toughness. These results will inform the design of similar alloys for use at high temperatures. (c) 2021 Elsevier B.V. All rights reserved.

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