Materials Characterization ( IF 3.562 ) Pub Date : 2020-03-07 , DOI: 10.1016/j.matchar.2020.110265
Z.H. Li, J.K. Ren, C. Wang, X. Wang, R.D.K. Misra, G.D. Wang

A novel advanced high-strength steel Fe79.85Cr2.07Ni2.62Si2.68B0.5Mn12C0.23 (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 M2B boride was confirmed to be of bcc crystal structure and exhibited ${\left(1\overline{1}2\right)}_{\mathrm{M}2\mathrm{B}}//{\left(200\right)}_{\gamma }$, ${\left[\overline{1}11\right]}_{\mathrm{M}2\mathrm{B}}//{\left[011\right]}_{\gamma }$ 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.

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