Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 737, Issue -, Pages 69-76Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2018.09.024
Keywords
Austenitic steel; TRIP and TWIP mechanisms; Mn-segregation; Recrystallization; Mechanical properties
Categories
Funding
- POSCO (Pohang Iron and Steel Company) [2016Y029]
- Brain Korea 21 PLUS Project for Center for Creative Industrial Materials
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Austenitic high-Mn steels have been nominated as potential alloys for ultra-high strength and excellent ductility, but the high-Mn content inevitably generates band-shaped Mn-segregation due to dendritic solidification from the steel melt. This segregation band often causes unintended deformation mechanisms and anisotropic mechanical properties, and deteriorates formability. Here, we effectively utilize the Mn-segregated bands for the improvement of tensile properties by actively producing TWinning- and TRansformation-induced plasticity (TWIP and TRIP) mechanisms in high- and low-Mn-segregated bands. We also adopt a mixed microstructure of non-recrystallized and recrystallized austenite mainly formed in high- and low-Mn-segregated bands, respectively. The TWIP + TRIP mechanisms generating highly-sustained strain hardening and high strain hardening, coupled with partial recrystallization and precipitation hardening, are working successfully for overcoming lowyield-strength characteristics of austenite to reach 1 GPa and for achieving the excellent tensile strength of 1.5 GPa and ductility of 44%. Our results demonstrate how the Mn-segregation-induced TWIP +TRIP mechanisms can be a novel idea in ultra-high-strength steel design.
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