TY - JOUR
T1 - Exceptional combination of ultra-high strength and excellent ductility by inevitably generated Mn-segregation in austenitic steel
AU - Jo, Min Chul
AU - Lee, Hyungsoo
AU - Zargaran, A.
AU - Ryu, Joo Hyun
AU - Sohn, Seok S
AU - Kim, Nack J.
AU - Lee, Sunghak
PY - 2018/11/8
Y1 - 2018/11/8
N2 - 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 low-yield-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.
AB - 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 low-yield-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.
KW - Austenitic steel
KW - Mechanical properties
KW - Mn-segregation
KW - Recrystallization
KW - TRIP and TWIP mechanisms
UR - http://www.scopus.com/inward/record.url?scp=85053432125&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85053432125&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2018.09.024
DO - 10.1016/j.msea.2018.09.024
M3 - Article
AN - SCOPUS:85053432125
VL - 737
SP - 69
EP - 76
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
ER -