A new hot-rolled alloy of carbide-free bainite has been proposed for heavy trucks frames. It involves dynamic bainite transformation during the prolonged cooling of the coiling process after hot-rolling. The new hot-rolled Fe-0.5C-2.9Mn-2.3Al (in wt-%) steels exhibit tensile strength of 1110 MPa with a combined total elongation of 35%. The alloy has been re-heat-treated with one step and two steps isothermal bainitic transformation to study the effect of microstructure evolution and microstructure-property relationship. The transformation-induced plasticity (TRIP) effect of retained austenite has been discussed and revealed as the main contributor for the high ductility of bainitic steels. The formation of the cracks at fracture regions after tensile deformation, which is associated with the austenite stability and morphology, has been observed and discussed.
NonakaTTaniguchiHGotoKDevelopment of ultra-high-strength cold-rolled steel sheets for automotive use. Nippon Steel Tech Report. 2003; 88:13–15.
2.
YiHLSunLXiongXC.Challenges in the formability of the next generation of automotive steel sheets. Mater Sci Technol. 2018; 34(9):1112–1117.
3.
SpeerJGDe MoorEFindleyKOAnalysis of microstructure evolution in quenching and partitioning automotive sheet steel. Metall Mater Trans A. 2011; 24:3591–3601.
4.
FengWJWuZBWangLEffect of testing temperature on retained austenite stability of cold rolled C-Mn-Si steels treated by quenching and partitioning process. Steel Research Inter. 2013; 84:246–252.
5.
SuhDWParkSJLeeTHInfluence of Al on the microstructural evolution and mechanical behavior of low-carbon, manganese transformation-induced-plasticity steel. Metall Mater Trans A. 2010; 41(2):397.
6.
HuJCaoWQHuangCXCharacterization of microstructures and mechanical properties of cold-rolled medium-Mn steels with different annealing processes. ISIJ Inter. 2015; 55:2229–2236.
7.
YiHLChenPBhadeshiaHKDH.Optimizing the morphology and stability of retained austenite in a δ-TRIP steel. Metall Mater Trans A. 2014; 45:3512–3518.
8.
ChatterjeeSMurugananthMBhadeshiaHKDH.δ-TRIP steel. Mater Sci Technol. 2007; 23:819–827.
9.
XiongXCChenBHuangMXThe effect of morphology on the stability of retained austenite in a quenched and partitioned steel. Scripta Mater. 2013; 68(5):321–324.
10.
XiXHWangJLLiXThe role of intercritical annealing in enhancing low-temperature toughness of Fe-C-Mn-Ni-Cu structural steel. Metall Mater Trans A. 2019; 50:2912–2921.
11.
SunJYuH.Microstructure development and mechanical properties of quenching and partitioning (Q&P) steel and an incorporation of hot-dipping galvanization during Q&P process. Mater Sci Eng A. 2013; 586:100–107.
12.
ShimizuTFunakawaYKanekoS.High strength steel sheets for automobile suspension and chassis use – high strength hot-rolled steel sheets with excellent press formability and durability for critical safety parts. JFE Tech Report. 2004; 4:25–31.
13.
LiJ.Effects of welding current on microstructure and properties of welding joint for 710L steel. Agric Equip Veh Eng. 2016; 54:52–54, 57.
14.
DuXTWangBKDuanZFApplication of high strength beam steel for automobile on frame lightweight of heavy truck. Phys Examination Test. 2016; 34:15–19.
15.
Morales-RivasLRoelofsHHaslerSComplex microstructural banding of continuously cooled carbide-free Bainitic steels. Mater Sci Forum. 2014; 783-786:980–985.
16.
BhadeshiaHKDH.Nanostructured bainite. Proc R Soc A Math Phys Eng Sci. 2009; 466:3–18.
17.
LongXYZhangFCKangJLow-temperature bainite in low-carbon steel. Mater Sci Eng A. 2014; 594:344–351.
18.
EfremenkoVShimizuKZurnadgyVMechanical properties of carbide-free lower bainite in complex-alloyed constructional steel: effect of bainitizing treatment parameters. Kovove Mater. 2020; 58:129–140.
19.
HaseKGarcia-MateoCBhadeshiaHKDH.Bimodal size-distribution of bainite plates. Mater Sci Eng A. 2006; 438-440:145–148.
20.
DuongVTSongYYParkKSAustenite in transformation-induced plasticity steel subjected to multiple isothermal heat treatments. Metall Mater Trans A. 2014; 45(10):4201–4209.
21.
BhadeshiaHKDH.Bainite in steels: transformations, microstructure and properties. London: IOM Communications; 2001.
22.
BhadeshiaHKDHHoneycombeSR.The effects of alloying elements on iron-carbon alloys. Steels. 2006: 71–93.
23.
BrackeLXuW.Effect of the Cr content and coiling temperature on the properties of hot rolled high strength lower bainitic steel. ISIJ Int. 2015; 55(10):2206–2211.
24.
ZhaoJLZhaoXMZhaoXYEffects of nucleation site and morphology of carbide-free bainite on microstructures and properties of bainite/martensite multi-phase steels. Mater Sci Eng A. 2019; 744:86–93.
25.
TsaiYTChangHTHuangBMMicrostructural characterization of Charpy-impact-tested nanostructured bainite. Mater Charact. 2015; 107:63–69.
26.
TsaiYTLinCRLeeWSMechanical behavior and microstructural evolution of nanostructured bainite under high-strain rate deformation by Hopkinson bar. Scripta Mater. 2016; 115:46–51.
27.
SugimotoKIUsuiNKobayashiMEffects of volume fraction and stability of retained austenite on ductility of TRIP-aided dual-phase steels. ISIJ Inter. 1992; 32:1311–1318.
28.
VandijkNHButtAMZhaoLThermal stability of retained austenite in TRIP steels studied by synchrotron X-ray diffraction during cooling. Acta Mater. 2005; 53:5439–5447.
29.
YuHCCaiZZRyomKBehavior of V-Ti elements in warm-rolled transformation-induced plasticity steel with medium manganese content. ISIJ Inter. 2020; 60(3):556–563.
30.
YangHSBhadeshiaHKDH.Austenite grain size and the martensite-start temperature. Scripta Mater. 2009; 60:493–495.
31.
YiHLLeeKYBhadeshiaHKDH.Mechanical stabilisation of retained austenite in δ-TRIP steel. Mater Sci Eng A. 2011; 52:5900–5903.
32.
ChenPWangGDCeguerraAVYield strength enhancement by carbon trapping in ferrite of the quenching and partitioning steel. Metall Mater Trans A. 2017; 49(1):235–240.
33.
BhadeshiaHKDH.Properties of fine-grained steels generated by displacive transformation. Mater Sci Eng A. 2008; 481:36–39.
34.
BhadeshiaHKDH.Nanostructured bainite, Proceedings of the Royal Society A: Mathematical. Phys Eng Sci. 2010; 466:3–18.
35.
AvishanBYazdaniSCaballeroFGCharacterisation of microstructure and mechanical properties in two different nanostructured bainitic steels. Mater Sci Technol. 2015; 31:1508–1520.
36.
YoungCHBhadeshiaHKDH.Computer modelling for the yield strength of the mixed micro-structures of bainite and martensite. J Phys IV. 1995; 5:266–272.
37.
Jacques PJFurnémontQLaniFMultiscale mechanics of TRIP-assisted multiphase steels: I. Characterization and mechanical testing. Acta Mater. 2007; 55(11):3681–3693.
38.
TanXDXuYBYangXLEffect of partitioning procedure on microstructure and mechanical properties of a hot-rolled directly quenched and partitioned steel. Mater Sci Eng A. 2014; 594:149–160.
39.
GuoHZhaoADingRQuenching and partitioning steel produced through hot rolling, direct quenching and annealing. Mater Sci Technol. 2016; 32:1605–1612.
40.
LiYJLiXLYuanGMicrostructure and partitioning behavior characteristics in low carbon steels treated by hot-rolling direct quenching and dynamical partitioning processes. Mater Charact. 2016; 121:157–165.
41.
LiYJChenDKangJKinetics of carbon partitioning during non-isothermaltreatment and mechanical properties of the first Industrial coils of hot rolled quenched and partitioned steel. Steel Res Inter. 2019; 90:1–11.
42.
LeeYKHanJH.Current opinion in medium manganese steel. Mater Sci Technol. 2014; 31:843–856.
43.
HellJCDehmasMAllainSMicrostructure-properties relationships in carbide-free bainitic steels. ISIJ Inter. 2011; 51:724–1732.
HellJCHazotteAChateauJPCMicrostructural and mechanical characterizations of carbide-free bainitic steels; 2010; Canada): Mcmaster's Workshop Conference; 2010.
46.
CuiWFZhangSXJiangYMechanical properties and hot-rolled microstructures of a low carbon bainitic steel with Cu–P alloying. Mater Sci Eng A. 2011; 528(21):6401–6406.
47.
WangYZhangKGuoZHA new effect of retained austenite on ductility enhancement in high strength bainitic steel. Mater Sci Eng A. 2012; 552(34):288–294.
48.
LeeHKohHJSeoCHMicrostructure and tensile properties of hot-rolled Fe-C-Mn-Si-Cu multiphase steel. Scripta Mater. 2008; 59(1):83–86.
49.
VarshneyASangalSKunduSSuper strong and highly ductile low alloy multiphase steels consisting of bainite, ferrite and retained austenite. Mater Design. 2016; 95:75–88.
50.
WangXLWuKMHuFMulti-step isothermal bainitic transformation in medium-carbon steel. Scripta Mater. 2014; 74(3):56–59.
