Effect of elemental segregation and minor phase on mechanical properties of as-cast super-thick steels studied using in-situ synchrotron X-ray and neutron diffraction

Abstract

Internal defects, especially those caused by elemental segregation and minor phases in as-cast super-thick steel plates with large section sizes, can critically impact the subsequent manufacturing processes and the mechanical properties of final products, which may result in catastrophic failure during industrial applications. However, the effects of elemental segregation and the resultant phase structures on deformation behaviors and real-time microstructural evolution under tensile loading remain unexplored in as-cast super-thick steels. In this study, we employed in-situ synchrotron and neutron diffraction techniques during tensile tests to investigate the relationship between internal defects and deformation behaviors of segregated and non-segregated super-thick steels. Compared to the segregated sample, the non-segregated sample exhibited improved yield and tensile strengths, increasing from 407.5 and 590.5 MPa to 515.2 and 632.8 MPa, respectively, with a significant increase in elongation from 8% to 23.4%. Strip-like elemental segregations were observed in the central core area due to final solidification, and the stress partitioning between ferrite matrix and retained austenite was revealed to be beneficial for uniform plastic deformation and necking before fracture. Both ductile and brittle fractographies were identified in segregated conditions. Our findings address a critical knowledge gap in understanding how elemental segregation and minor phases affect deformation behaviors, and offer valuable insights for optimizing processing parameters for as-cast super-thick steels.

Keywords

Elemental segregation / stress partitioning / in-situ synchrotron and neutron diffraction / super-thick steels

References

[1] Yu K,Fan H,Ren Z.Investigation on the solidification structure of Q355 in 475 mm extra-thick slabs adopting cellular automaton-finite element model.Metals2024;14:1012

[2] Guthrie RIL.Continuous casting practices for steel: past, present and future.Metals2022;12:862

[3] Okayama Y,Yasui H. Production of high quality extra heavy plates with new casting equipment. Nippon Steel Technical Report; 2004. Available from: https://www.nipponsteel.com/en/tech/report/nsc/pdf/n9012.pdf [Last accessed on 7 Jul 2025]

[4] Li H,Li T,Wang G.Effects of hot-core heavy reduction rolling during continuous casting on microstructures and mechanical properties of hot-rolled plates.J Mater Proc Technol2020;283:116708

[5] Barati H,Kharicha A.Role of solidification in submerged entry nozzle clogging during continuous casting of steel.Steel Res Int2020;91:2000230

[6] Yang N,Wang X.Research on damage evolution in thick steel plates.J Constr Steel Res2016;122:213-25

[7] Cheng R,Zhang L.Comparison of porosity alleviation with the multi-roll and single-roll reduction modes during continuous casting.J Mater Proc Technol2019;266:96-104

[8] Brimacombe JK.Crack formation in the continuous casting of steel.Metall Trans B1977;8:489-505

[9] Fan K,Liu T,Belyakov A.Making large-size fail-safe steel by deformation-assisted tempering process.Sci Rep2024;14:22345 PMCID:PMC11437021

[10] Li H,Li R,Wang Z.Effect of a novel hot-core heavy reduction rolling process after complete solidification on deformation and microstructure of casting steel.ISIJ Int2019;59:2283-93

[11] Wang Q,Tian Y,Wang Z.Superior through-thickness homogeneity of microstructure and mechanical properties of ultraheavy steel plate by advanced casting and quenching technologies.Steel Res Int2021;92:2000698

[12] Jokiaho T,Peura P.Role of steel plate thickness on the residual stress formation and cracking behavior during flame cutting.Metall Mater Trans A2019;50:4178-92

[13] Ji C,Zhu M.Thermo-mechanical behavior of the continuous casting bloom in the heavy reduction process.JOM2016;68:3107-15

[14] Liu D,Chen Y.Strengthening and toughening of a heavy plate steel for shipbuilding with yield strength of approximately 690 MPa.Metall Mater Trans A2013;44:440-55

[15] Wang W,Liu H.Hot deformation behavior of a marine engineering steel for novel 980 MPa grade extra-thick plate.Steel Res Int2024;95:2300642

[16] Xie B,Yun Y,Ning Z.Development of high strength ultra-heavy plate processed with gradient temperature rolling, intercritical quenching and tempering.Mater Sci Eng A2017;680:454-68

[17] Hu J,Xie H,Misra R.Microstructure and mechanical properties of TMCP heavy plate microalloyed steel.Mater Sci Eng A2014;607:122-31

[18] Sun X,Xie Z,Shang C.Microstructure-property relationship in a high strength-high toughness combination ultra-heavy gauge offshore plate steel: the significance of multiphase microstructure.Mater Sci Eng A2017;689:212-9

[19] Chu R,Fan Y,Ma C.Cracking and segregation in high-alloy steel 0.4C1.5Mn2Cr0.35Mo1.5Ni produced by thick continuous casting.Heliyon2019;5:e01329 PMCID:PMC6416655

[20] Cao Y,Fu P.Distinct mechanisms for channel segregation in ultra-heavy advanced steel ingots via numerical simulation and experimental characterization.Metall Mater Trans B2023;54:2771-83

[21] Cameron R.Ultrasonic inspection for long defects in thick steel components.Int J Pres Ves Pip1985;18:255-76

[22] Choudhary S,Sengupta A.Solidification morphology and segregation in continuously cast steel slab.J Mater Proc Technol2017;243:312-21

[23] Ying H,He H.Formation of strong and ductile FeNiCoCrB network-structured high-entropy alloys by fluxing.Microstructures2023;3:2023018

[24] Dong B,Zhu H.Low neutron cross-section FeCrVTiNi based high-entropy alloys: design, additive manufacturing and characterization.Microstructures2022;2:2022003

[25] Wang Y,Harjo S,Ohmura T.In-situ neutron diffraction during tension-compression cyclic deformation of a pearlite steel.Mater Sci Eng A2016;676:522-30

[26] Sparks T,Gorley M.In-situ synchrotron investigation of elastic and tensile properties of oxide dispersion strengthened EUROFER97 steel for advanced fusion reactors.Acta Mater2024;271:119876

[27] Zhang X,Chen Y.High-energy synchrotron X-ray study of deformation-induced martensitic transformation in a neutron-irradiated type 316 stainless steel.Acta Mater2020;200:315-27

[28] Chen H,Nie Z.Unprecedented non-hysteretic superelasticity of [001]-oriented NiCoFeGa single crystals.Nat Mater2020;19:712-8

[29] Liu Z,Zheng T.A mechanism on multiscale heterogenous deformation of nickel-based single crystal superalloys unraveled by time-of-flight neutron diffraction technology.Acta Mater2024;281:120430

[30] Ma L,Nie Z.Reversible deformation-induced martensitic transformation in Al_0.6CoCrFeNi high-entropy alloy investigated by in situ synchrotron-based high-energy X-ray diffraction.Acta Mater2017;128:12-21

[31] Song C,Lu J,Yang S.Stress partitioning among ferrite, martensite and retained austenite of a TRIP-assisted multiphase steel: an in-situ high-energy X-ray diffraction study.Mater Sci Eng A2018;726:1-9

[32] Ding F,Hu B.Influence of softening annealing on microstructural heredity and mechanical properties of medium-Mn steel.Microstructures2022;2:2022009

[33] Gao F,Zhu Q,Liu Z.Deformation behavior of retained austenite and its effect on plasticity based on in-situ EBSD analysis for transformable ferritic stainless steel.J Mater Res Technol2022;20:1976-92