TY - JOUR
T1 - Effects of solute segregation on tensile properties and serration behavior in ultra-high-strength high-Mn TRIP steels
AU - Jo, Min Chul
AU - Choi, Jin Hyeok
AU - Lee, Hyungsoo
AU - Zargaran, A.
AU - Ryu, Joo Hyun
AU - Sohn, Seok Su
AU - Kim, Nack J.
AU - Lee, Sunghak
N1 - Funding Information:
This work was supported by POSCO under a contract No. 2016Y029 and by Brain Korea 21 PLUS Project for Center for Creative Industrial Materials. S.S. Sohn is grateful to the kind support of the Alexander von Humboldt Stiftung (AvH, Alexander von Humboldt Foundation, https://www.humboldt –foundation.de).
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2019/1/7
Y1 - 2019/1/7
N2 - Austenitic high-Mn TWinning- and Transformation-Induced Plasticity (TWIP and TRIP) steels are strong candidates for GPa-grade cold-rolled steel sheets. The reduction in C or Mn content from high-Mn TWIP steels help generate a TRIP mechanism and prevent serration. However, these high-Mn TRIP steels show low yield strength because of the inherent characteristics of austenite, and often contain a band-shaped segregation of solutes, making the steels acts as hetero-structural materials. Therefore, in this study, we investigate the effects of compositionally-segregated microstructures on tensile properties and serration behavior in precipitation-hardened high-Mn TRIP steels. The present TRIP steels showed high yield strength (778–824 MPa) and an excellent strength-ductility balance, along with serration in their stress-strain curves which could not be explained by existing theories of dynamic strain aging. A considerable amount of martensite was formed step by step as localized deformation bands passed through the specimen gage section, which implied that the serration occurred only when the transformation rate increased substantially. In microstructural aspects, the martensitic transformation occurred sequentially along Mn-segregated bands due to differences in austenite stability and Mn content between high- and low-Mn bands, thereby leading to discontinuous transformation and consequently the serrated flow.
AB - Austenitic high-Mn TWinning- and Transformation-Induced Plasticity (TWIP and TRIP) steels are strong candidates for GPa-grade cold-rolled steel sheets. The reduction in C or Mn content from high-Mn TWIP steels help generate a TRIP mechanism and prevent serration. However, these high-Mn TRIP steels show low yield strength because of the inherent characteristics of austenite, and often contain a band-shaped segregation of solutes, making the steels acts as hetero-structural materials. Therefore, in this study, we investigate the effects of compositionally-segregated microstructures on tensile properties and serration behavior in precipitation-hardened high-Mn TRIP steels. The present TRIP steels showed high yield strength (778–824 MPa) and an excellent strength-ductility balance, along with serration in their stress-strain curves which could not be explained by existing theories of dynamic strain aging. A considerable amount of martensite was formed step by step as localized deformation bands passed through the specimen gage section, which implied that the serration occurred only when the transformation rate increased substantially. In microstructural aspects, the martensitic transformation occurred sequentially along Mn-segregated bands due to differences in austenite stability and Mn content between high- and low-Mn bands, thereby leading to discontinuous transformation and consequently the serrated flow.
KW - Austenitic high-Mn steel
KW - Segregation
KW - Serration
KW - Transformation-Induced Plasticity (TRIP)
KW - Twinning-Induced Plasticity (TWIP)
UR - http://www.scopus.com/inward/record.url?scp=85055327038&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2018.10.065
DO - 10.1016/j.msea.2018.10.065
M3 - Article
AN - SCOPUS:85055327038
SN - 0921-5093
VL - 740-741
SP - 16
EP - 27
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
ER -