Yan Zhao

A novel lean duplex stainless steel (DSS) with excellent hot workability is successfully developed, referred as 21Cr‐DSS. The strain partitioning and softening mechanisms of the constituent phases in the novel steel are elucidated and compared with the conventional DSS. The strain is preferentially accommodated in the soft ferrite phase, leading to the significant strain localization and a faster restoration of dynamic recovery and dynamic recrystallization (DRV or DRX) in ferrite, whereas conventional DSS is characterized by inhomogeneity in softening and incompatibility in deformation between ferrite and austenite, which promotes the propagation of cracks along the δ/γ interface during hot deformation. However, the novel 21Cr‐DSS exhibits homogeneous strain–stress partitioning in δ/γ, especially at low deformation temperature, resulting in superior deformation compatibility between ferrite and austenite.

The thin strip of novel TRIP‐aided Ni‐free lean duplex stainless steel with good corrosion resistance is fabricated by twin‐roll strip casting. The microstructure, corrosion resistance, and mechanical properties of the present Ni‐free steel (DSS‐2) are investigated in detail in this study. Meanwhile, comparison with duplex stainless steel containing about 2% Ni (DSS‐1) is also conducted to discuss the effect of alloying Ni on corrosion resistance and mechanical properties. The DSS‐2 has the more excellent mechanical properties than the comparison steel DSS‐1 due to the strain induced martensitic transformation during plastic deformation, which the ultimate tensile strength and total elongation are measured to be about 960 MPa and 55%, respectively. The strain induced martensitic transformation in DSS‐2 will be suppressed with the increase of solid solution treatment temperature and strain rate. The austenitic stability is more dependent on element partitioning in austenite phase than on grain size of austenite for the present TRIP‐aided Ni‐free lean duplex stainless steel. The novel Ni‐free steel has the better corrosion resistance and mechanical properties than the austenitic stainless steel SUS304, which may potentially be applied to substitute SUS304 in some fields as anti‐corrosive structural material.