The present work simplifies the previous room-temperature quenching and partitioning (RT Q&P) process down to a single furnace cooling process, delivering a medium Mn steel with an ultimate tensile strength (UTS) of 1.7 GPa and a uniform elongation of 9.5%. The martensite tempering during furnace cooling is featured with slightly reduced dislocation density and is free of cementite precipitation, which is beneficial for ultrahigh UTS. Although the carbon partitioning is limited, the banded large austenite grains have proper mechanical stability owing to pre-existing high carbon content and the strong martensite matrix, allowing the gradual transformation-induced plasticity (TRIP) effect to enhance the work hardening behaviour and thus the good uniform elongation.
HeBB, HuB, YenHW, . High dislocation density-induced large ductility in deformed and partitioned steels. Science. 2017;357:1029–1032.
2.
HuangC, HuC, LiuY, . Recent developments and perspectives of advanced high-strength medium Mn steel: from material design to failure mechanisms. Mater Futures. 2022;1:32001.
3.
HeBB, ZhuK, HuangMX.On the nanoindentation behaviour of complex ferritic phases. Phil Mag Lett. 2014;94:439–446.
4.
TaylorT, FourlarisG, EvansP, . New generation ultrahigh strength boron steel for automotive hot stamping technologies. Mater Sci Tech. 2014;30:818–826.
5.
LiS, WenP, LiS, . A novel medium-Mn steel with superior mechanical properties and marginal oxidization after press hardening. Acta Mater2021;205:116567.
6.
HouZR, OpitzT, XiongXC, . Bake-partitioning in a press-hardening steel. Scripta Mater.2019;162:492–496.
7.
SpeerJ, MatlockDK, De CoomanBC, . Carbon partitioning into austenite after martensite transformation. Acta Mater. 2003;51:2611–2622.
8.
TanX, PongeD, LuW, . Carbon and strain partitioning in a quenched and partitioned steel containing ferrite. Acta Mater. 2019;165:561–576.
9.
EdmondsDV, HeK, RizzoFC, . Quenching and partitioning martensite – a novel steel heat treatment. Mat Sci Eng A. 2006;438:25–34.
10.
HeBB, LuoHW, HuangMX.Experimental investigation on a novel medium Mn steel combining transformation-induced plasticity and twinning-induced plasticity effects. Int J Plasticity. 2016;78:173–186.
11.
KraussG.Martensite in steel: strength and structure. Mat Sci Eng A. 1999;273-275:40–57.
12.
MatsudaH, MizunoR, FunakawaY, . Effects of auto-tempering behaviour of martensite on mechanical properties of ultra high strength steel sheets. J Alloy Compd. 2013;577:S661–S667.
13.
NishibataT, KojimaN.Effect of quenching rate on hardness and microstructure of hot-stamped steel. J Alloy Compd. 2013;577:S549–S554.
14.
JarvinenH, IsakovM, NyyssonenT, . The effect of initial microstructure on the final properties of press hardened 22MnB5 steels. Mat Sci Eng A.2016;676:109–120.
15.
ZurnadzhyVI, EfremenkoVG, WuKM, . Tailoring strength/ductility combination in 2.5 wt% Si-alloyed middle carbon steel produced by the two-step Q-P treatment with a prolonged partitioning stage. Mat Sci Eng A. 2020;791:139721.
16.
PierceDT, CoughlinDR, ClarkeKD, . Microstructural evolution during quenching and partitioning of 0.2C-1.5Mn-1.3Si steels with Cr or Ni additions. Acta Mater. 2018;151:454–469.
17.
HeBB, WangM, HuangMX.Improving tensile properties of room-temperature quenching and partitioning steel by dislocation engineering. Metall Mater Trans A. 2019;50:4021–4026.
18.
HeBB, LiuL, HuangMX.Room-temperature quenching and partitioning steel. Metall Mater Trans A. 2018;49A:3167–3172.
19.
HeBB, WangM, LiuL, . High-strength medium Mn quenching and partitioning steel with low yield ratio. Mater Sci Tech. 2019;35:2109–2114.
20.
PanS, HeB.On the variants of thermal process in developing strong and ductile medium Mn steel. Front Mater. 2020;7:256.
21.
HeBB, PanS, HuangMX.Extra work hardening in room-temperature quenching and partitioning medium Mn steel enabled by intercritical annealing. Mat Sci Eng A. 2020;797:140106.
22.
LiuL, HeBB, ChengGJ, . Optimum properties of quenching and partitioning steels achieved by balancing fraction and stability of retained austenite. Scripta Mater. 2018;150:1–6.
23.
KrbataM, KrizanD, EckertM, . Austenite decomposition of a lean medium Mn steel suitable for quenching and partitioning process: comparison of CCT and DCCT diagram and their microstructural changes. Materials. 2022;15:1753.
24.
BardelcikA, SalisburyCP, WinklerS, . Effect of cooling rate on the high strain rate properties of boron steel. Int J Impact Eng. 2010;37:694–702.
25.
UngárT.Microstructural parameters from X-ray diffraction peak broadening. Scripta Mater. 2004;51:777–781.
26.
UngarT, DragomirI, ReveszA, . The contrast factors of dislocations in cubic crystals: the dislocation model of strain anisotropy in practice. J Appl Crystallogr. 1999;32:992–1002.
27.
UngarT, GubiczaJ, RibarikG, . Crystallite size distribution and dislocation structure determined by diffraction profile analysis: principles and practical application to cubic and hexagonal crystals. J Appl Crystallogr. 2001;34:298–310.
28.
UngárT, BorbélyA.The effect of dislocation contrast on X-ray line broadening: a new approach to line profile analysis. Appl Phys Lett. 1996;69:3173–3175.
29.
LiY, GuanQ, HeB.Improving the strength and ductility of medium Mn steel by depleting the stress-assisted martensite. Scripta Mater. 2023;226:115267.
30.
KraussG.Solidification, segregation, and banding in carbon and alloy steels. Metall Mater Trans B. 2003;34:781–792.
31.
HajyAkbaryF, SietsmaJ, PetrovRH, . A quantitative investigation of the effect of Mn segregation on microstructural properties of quenching and partitioning steels. Scripta Mater. 2017;137:27–30.
32.
HeBB.On the factors governing austenite stability: intrinsic versus extrinsic. Materials. 2020;13:3440.
33.
MahieuJ, MakiJ, De CoomanBC, . Phase transformation and mechanical properties of Si-free CMnAl transformation-induced plasticity-aided steel. Metall Mater Trans A. 2002;33:2573–2580.
34.
Jimenez-MeleroE, van DijkNH, ZhaoL, . Characterization of individual retained austenite grains and their stability in low-alloyed TRIP steels. Acta Mater. 2007;55:6713–6723.
35.
KraussG, MarderAR.The morphology of martensite in iron alloys. Metall Trans. 1971;2:2343–2357.
36.
MartenssonH.The effect of the transformation substructure on the mechanical properties of a low-carbon, manganese martensitic steel. Metall Trans. 1971;2:3490–3492.
37.
DongJ, ZhouX, LiuY, . Carbide precipitation in Nb-V-Ti microalloyed ultra-high strength steel during tempering. Mat Sci Eng A. 2017;683:215–226.
38.
GunduzS, CochraneRC.Influence of cooling rate and tempering on precipitation and hardness of vanadium microalloyed steel. Mater Design. 2005;26:486–492.
39.
AtasoyOA, OzbaysalK, InalOT.Precipitation of vanadium carbides in 0.8% C-13% Mn-1% V austenitic steel. J Mater Sci. 1989;24:1393–1398.
40.
HarrisSJ, NagNR.Effect of warm working on the precipitation of vanadium carbide in a medium carbon austenitic steel. J Mater Sci. 1976;11:1320–1329.
41.
RoitburdAL, KurdjumovGV.The nature of martensitic transformations. Mat Sci Eng A. 1979;39:141–167.
42.
CalcagnottoM, AdachiY, PongeD, . Deformation and fracture mechanisms in fine- and ultrafine-grained ferrite/martensite dual-phase steels and the effect of aging. Acta Mater. 2011;59:658–670.
43.
ShiJ, SunX, WangM, . Enhanced work-hardening behavior and mechanical properties in ultrafine-grained steels with large-fractioned metastable austenite. Scripta Mater. 2010;63:815–818.
44.
WilliamsonGK, HallWH.X-ray line broadening from filed aluminium and wolfram. Acta Metall. 1953;1:22–31.
45.
HajyAkbaryF, SietsmaJ, BottgerAJ, . An improved X-ray diffraction analysis method to characterize dislocation density in lath martensitic structures. Mat Sci Eng A. 2015;639:208–218.
46.
MoritoS, YoshidaH, MakiT, . Effect of block size on the strength of lath martensite in low carbon steels. Mat Sci Eng A. 2006;438-440:237–240.
47.
HeBB, HuangMX.Revealing the intrinsic nanohardness of lath martensite in low carbon steel. Metall Mater Trans A. 2015;46:688–694.
48.
OliverWC, PharrGM.An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J Mater Res. 1992;7:1564–1583.
49.
TaylorGI.The mechanism of plastic deformation of crystals. Part I. Theoretical. Proc R Soc A. 1934;145:362–387.
50.
van DijkNH, ButtAM, ZhaoL, . Thermal stability of retained austenite in TRIP steels studied by synchrotron X-ray diffraction during cooling. Acta Mater. 2005;53:5439–5447.
51.
LiuL, HeBB, HuangMX.The role of transformation-induced plasticity in the development of advanced high strength. Adv Eng Mater. 2018;20:1701083.
52.
FahrD.Stress-and strain-induced formation of martensite and its effects on strength and ductility of metastable austenitic stainless steels. Metall Trans. 1971;2:1883–1892.
53.
YangH, BhadeshiaH.Austenite grain size and the martensite-start temperature. Scripta Mater. 2009;60:493–495.
54.
XiongXC, ChenB, HuangMX, . The effect of morphology on the stability of retained austenite in a quenched and partitioned steel. Scripta Mater. 2013;68:321–324.
55.
JacquesPJ, LadriereJ, DelannayF.On the influence of interactions between phases on the mechanical stability of retained austenite in transformation-induced plasticity multiphase steels. Metall Mater Trans A. 2001;32:2759–2768.
56.
HeBB, HuangMX.On the mechanical stability of austenite matrix after martensite formation in a medium Mn steel. Metall Mater Trans A. 2016;47A:3346–3353.
57.
HeSH, HeBB, ZhuKY, . Revealing the role of dislocations on the stability of retained austenite in a tempered bainite. Scripta Mater. 2019;168:23–27.
58.
Marceaux Dit ClémentA, HoummadaK, DrilletJ, . Effects of cementite size and chemistry on the kinetics of austenite formation during heating of a high-formability steel. Comp Mater Sci.2020;182:109786.
59.
GuoQ, YenH, LuoH, . On the mechanism of Mn partitioning during intercritical annealing in medium Mn steels. Acta Mater. 2022;225:117601.
60.
BansalGK, RajinikanthV, GhoshC, . Microstructure-property correlation in low-Si steel processed through quenching and nonisothermal partitioning. Metall Mater Trans A. 2018;49A:3501–3514.
61.
BansalGK, RajinikanthV, GhoshC, . Effect of cooling rate on the evolution of microstructure and mechanical properties of nonisothermally partitioned steels. Mat Sci Eng A. 2020;788:139614.
62.
LiYJ, LiuD, ChenD, . Response of retained austenite to quenching temperature in a novel low density Fe-Mn-Al-C steel processed by hot rolling-air cooling followed by non-isothermal partitioning. Mat Sci Eng A. 2019;753:197–207.
63.
LiY, LiX, YuanG, . Microstructure and partitioning behavior characteristics in low carbon steels treated by hot-rolling direct quenching and dynamical partitioning processes. Mater Charact. 2016;121:157–165.
64.
BansalGK, JenaPSM, GhoshC, . Quench temperature-dependent mechanical properties during nonisothermal partitioning. Metall Mater Trans A. 2020;51:5088–5100.
65.
LiYJ, KangJ, ZhangWN, . A novel phase transition behavior during dynamic partitioning and analysis of retained austenite in quenched and partitioned steels. Mat Sci Eng A. 2018;710:181–191.
