Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 885, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2023.145602
Keywords
Lightweight steel; Microstructural evolution; Recrystallization; & kappa;-carbide; Mechanical properties
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By partial-recrystallization annealing and short aging treatment, the microstructure of cold-rolled lightweight steel is optimized, with nanosized α-carbides and non-recrystallized austenite grains containing dense dislocations. As a result, the steel exhibits high yield strength and excellent ductility.
The introduction of dislocations and nanoprecipitates effectively enhances the mechanical properties of lightweight steel. Herein, cold-rolled lightweight steel was processed through partial-recrystallization annealing and subsequent short aging to achieve a microstructure comprising fine recrystallized grains containing nanosized ?-carbides and non-recrystallized austenite grains containing dense dislocations and nanosized ?-carbides. Thus, the steel exhibited a high yield strength of 1363 MPa, which was primarily attributed to the fine-grain strengthening from the recrystallized austenite grains, dislocation strengthening from the non-recrystallized austenite grains, and precipitation strengthening from the nanosized ?-carbides. Notably, even at this high yield strength, the steel exhibited excellent ductility, with a total elongation exceeding 25%. Moreover, the heterogeneous microstructure of the steel promoted rapid precipitation of ?-carbides during aging. The preexisting dislocations in the non-recrystallized austenite grains facilitated an accelerated diffusion of the constituent elements of the steel, effectively achieving precipitation strengthening of the ?-carbides. This prevented the precipitation of the intergranular ?-carbides around austenite grain boundaries due to over-aging, which could lead to a detrimental reduction in the ductility of the steel.
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