(110265)Design of a cold-rolled novel advanced high-strength steel: An analysis of microstructural evolution and mechanical properties

摘要

A novel advanced high-strength steel Fe_(79.85)Cr_(2.07)Ni_(2.62)Si_(2.68)B_(0.5)Mn_(12)Co_(.23) (wt%) was designed in laboratory scale. Steel microstructures under conditions of cast ingot, cold rolling, annealing and after tensile deformation were characterized by means of scanning electron microscopy, electron backscattered diffraction, X-ray diffraction and transmission electron microscopy. The corresponding mechanical properties were analyzed. Results showed that a high number density of nano-sized boride particles precipitated in austenite matrix, which contributed to grain refinement during annealing and deformation. The M_2B boride was confirmed to be of bcc crystal structure and exhibited (112)_(m2b)//(200)_γ, [111]_(M2b)//[011]_γ orientation relationships with austenite matrix. The differential C-J analysis was used to understand work-hardening behaviors of steel samples subjected to various annealing processes. It was indicated that the tensile deformation was divided into three stages and each stage was associated with a distinct work-hardening exponent n value. A good combination of tensile strength (1260 MPa) and elongation (25%) was achieved as a result of enhanced work hardening behavior concerning mechanisms of dislocation glide, strain-induced martensitic transformation and mechanical twinning.