Sunghak Lee
Pohang University of Science and Technology
Composite numberUltimate tensile strengthDeformation (engineering)Composite materialMartensiteMetallurgyMaterials scienceAlloyFracture mechanicsVolume fractionMicrostructureAusteniteFracture toughness
508Publications
65H-index
9,878Citations
Publications 509
Newest
#1Farahnaz Haftlang (POSTECH: Pohang University of Science and Technology)H-Index: 7
#2Peyman Asghari-Rad (POSTECH: Pohang University of Science and Technology)H-Index: 11
Last. Hyoung Seop KimH-Index: 64
view all 6 authors...
Abstract null null In the work reported here, the mechanical properties of a newly developed Fe-Ni-Co-Mn-Ti-Si medium-entropy alloy with heterogeneous microstructure were investigated. High yield strength (∼930 MPa), high ultimate tensile strength (∼1100 MPa), and good ductility (∼30%) were achieved using hetero-deformation-induced strengthening and high plastic-incompatibility between mechanically induced-martensite and the austenitic matrix.
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#1Dong Geun Kim (POSTECH: Pohang University of Science and Technology)H-Index: 9
#2Yong Hee JoH-Index: 14
Last. Sunghak Lee (POSTECH: Pohang University of Science and Technology)H-Index: 65
view all 7 authors...
Abstract null null When a high-entropy alloy (HEA) and an austenitic stainless steel (STS) are combined to produce a multi-layered sheet (MLS), the synergic effects of maximized body-centered-cubic(BCC) transformation-induced plasticity (TRIP) occurring in both HEA and STS on excellent tensile properties are expected. In this study, the tensile properties of STS/HEA/STS MLS, fabricated by hot-roll bonding, were compared with those of monolithic HEA and STS sheets. Both the HEA and STS layers of ...
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#1Seok Gyu Lee (POSTECH: Pohang University of Science and Technology)H-Index: 8
#2Yong Hee Jo (POSTECH: Pohang University of Science and Technology)H-Index: 14
Last. Sunghak Lee (POSTECH: Pohang University of Science and Technology)H-Index: 65
view all 7 authors...
Abstract null null In this study, a high-entropy-alloy-cored multi-layered sheet (MLS) clad with an austenitic high-Mn twinning-induced-plasticity steel (HEA/high-Mn MLS) is proposed and its room- and cryogenic-temperature tensile behaviors were investigated. The MLS was fabricated using a commercial roll-bonding procedure. Its interface was well bonded without critical defects such as pores or voids. During the MLS fabrication and subsequent annealing, the interdiffusion of alloying elements an...
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#1Yong Hee Jo (POSTECH: Pohang University of Science and Technology)H-Index: 14
#2Junha Yang (POSTECH: Pohang University of Science and Technology)H-Index: 4
Last. Sunghak Lee (POSTECH: Pohang University of Science and Technology)H-Index: 65
view all 9 authors...
Abstract We present a new class of metastable high-entropy alloys (HEAs), triggering deformation-induced martensitic transformation (DIMT) from face-centered-cubic (FCC) to body-centered-cubic (BCC), i.e., BCC-DIMT. Through the ab-initio calculation based on 1st order axial interaction model and combined with the Gibbs free energy calculation, the addition of Si is considered as a critical element which enables to reduce the intrinsic stacking fault energy (ISFE) in SixV(9-x)Cr10Mn5Fe46Co30 (x =...
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#1Jisung YooH-Index: 6
#2Min Chul Jo (Samsung)H-Index: 10
Last. Sunghak Lee (POSTECH: Pohang University of Science and Technology)H-Index: 65
view all 5 authors...
Abstract In this study, effects of Nb or (Nb + Mo) alloying into a 1.9-GPa-grade 32MnB5 press hardening steel on Charpy impact, bending, and delayed fracture properties were investigated. All the properties were enhanced in the Nb- or (Nb + Mo)-alloyed steels, especially in the (Nb + Mo)-alloyed steel. The Nb alloying worked for the precipitation of nano-sized complex carbides, thereby leading to the refinement of prior austenite grains by a Zener pinning effect. Mo also contributed to the grain...
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#1Jeong Min Park (POSTECH: Pohang University of Science and Technology)H-Index: 17
#2Dae Cheol Yang (KU: Korea University)H-Index: 2
Last. Seok Su Sohn (KU: Korea University)H-Index: 28
view all 7 authors...
An equiatomic VCoNi medium-entropy alloy possesses high sensitivity to grain-boundary strengthening, achieved by severe lattice distortions. Its ultrafine-grain structure enables 1.5 Gigapascal yie...
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#1Yong Hee Jo (POSTECH: Pohang University of Science and Technology)H-Index: 14
#2Dae Woong Kim (POSTECH: Pohang University of Science and Technology)H-Index: 7
Last. Sunghak Lee (POSTECH: Pohang University of Science and Technology)H-Index: 65
view all 4 authors...
Abstract Systematic investigation of microstructure characterization and mechanical property was performed on metastable Fe46Co30Cr10Mn5Si7V2 high-entropy alloy (HEA) with varying the grain size. The grain coarsening led to the decrease in stability of face-centered-cubic (FCC) phase, and consequently generated the formation of laminate-morphology hexagonal-close-packed (HCP) and butterfly-morphology body-centered-cubic (BCC) martensite. During the tensile test, a transformation-induced plastici...
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#1Dong Geun Kim (POSTECH: Pohang University of Science and Technology)H-Index: 9
#2Min Cheol Jo (POSTECH: Pohang University of Science and Technology)H-Index: 9
Last. Sunghak Lee (POSTECH: Pohang University of Science and Technology)H-Index: 65
view all 7 authors...
Abstract Room- and cryogenic-temperature compressive properties for the three V10Cr10Co30FexNi50-x (x=40, 45, 50) high entropy alloys are investigated under quasi-static and dynamic loading conditions. The face-centered cubic (FCC) stability, which is estimated by the calculation of Gibbs free energy difference between FCC and body-centered cubic (BCC) phases, decreases in increasing order of Fe content. The 40Fe and 45Fe alloys consist of FCC single phase, whereas the 50Fe alloy is composed of ...
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#1Jung Gi Kim (Gyeongsang National University)H-Index: 17
#2Jae Wung Bae (POSTECH: Pohang University of Science and Technology)H-Index: 22
Last. Hyoung Seop Kim (POSTECH: Pohang University of Science and Technology)H-Index: 64
view all 7 authors...
Heterogeneous structured materials achieve a combination of high strength and extreme ductility due to synergetic strengthening driven by conditions in the interfacial region. Although the origin of synergetic strengthening has been revealed to be strain incompatibility in the interfacial region, the effect of the strength difference between hard and soft phases on strengthening has not been investigated well. In the work reported in the present paper, the effect of the difference in strength of...
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