Effects of cold rolling on precipitation, microstructure and mechanical properties of super-ferritic stainless steels
Ling-Yun Du, Hui‐Hu Lu, Jianchun Li, Haitao Liu, Shuhai Zhang
Abstract
A hot rolled 27.6Cr-3.7Mo-2Ni super-ferritic stainless steel sheet was cold rolled and subsequently annealed over a wide temperature range of 600 to 1150 °C. The recovery, recrystallization, precipitation, and their effects on mechanical properties were investigated. Cold rolling deformation resulted in grain elongation along the rolling direction (RD), with predominant α-, η-, and γ-fiber textures. Microstructural analysis revealed that uniform deformation bands primarily formed in grains with α- and η-orientations, while shear bands preferentially developed in γ-oriented grains. After low-temperature annealing (<900 °C), the recovery was activated, accompanied by the formation of sub-grains along the shear bands, which served as recrystallization nuclei. Then, χ, σ and Laves phase were simultaneously observed. In contrast, high-temperature annealing (>900 °C) activated recrystallization nucleation through both shear band and sub-grain coalescence mechanisms. The σ and Laves phases were observed during annealing at 900–1000 °C, while only the Laves phase remained in samples annealed at 1050 °C. After annealing at 1050 °C, a layered recrystallized structure—composed of fine and coarse grain layers, both influenced by Laves phase precipitation—was obtained, along with a single γ-fiber texture exhibiting a peak at the {111}<112> component. Through controlled recrystallization and Laves phase precipitation, the cold-rolled samples annealed at 1050 °C achieved high ultimate tensile strength (597.5–610.0 MPa), yield strength (465.0–477.5 MPa), and significant elongation (21.0–24.7%).