An intercritical annealing pre-treatment was added before the conventional two-step heat treatment process, and the effect of the isothermal bainitic transformation (IBT) time on the steel's microstructure and mechanical properties were investigated. The microstructure was investigated using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, while the mechanical properties were evaluated using tensile testing. The microstructure of the three-step hot-dip galvanised transformation induced plasticity (TRIP) steel consists of ferrite, bainite, retained austenite, and martensite. The mechanical properties of the steel after the three-step heat treatment process are excellent, with a tensile strength above 770 MPa and elongation above 29%. The effect of IBT time on the mechanical properties was insignificant because the intercritical annealing pre-treatment increases the bainitic transformation rate.
ZhaoJ, JiangZ.Thermomechanical processing of advanced high strength steels. Prog Mater Sci. 2018;94:174–242. doi: 10.1016/j.pmatsci.2018.01.006
2.
JacquesPJ.Transformation-induced plasticity for high strength formable steels. Curr Opin Solid State Mater Sci. 2004;8:259–265. doi: 10.1016/j.cossms.2004.09.006
3.
JacquesP, DelannayF, CornetX, Enhancement of the mechanical properties of a low-carbon, low-silicon steel by formation of a multiphased microstructure containing retained Austenite. Metall Mater Trans A. 1998;29:2383–2393. doi: 10.1007/s11661-998-0114-1
4.
ChenHC, EraH, ShimizuM.Effect of phosphorus on the formation of retained austenite and mechanical properties in Si-containing low-carbon steel sheet. Metall Mater Trans A. 1989;20:437–445. doi: 10.1007/BF02653923
5.
MatsumuraO, SakumaY, TakechiH.TRIP and its kinetic aspects in austempered 0.4C-1.5Si-0.8Mn steel. Scr Metall. 1987;21:1301–1306. doi: 10.1016/0036-9748(87)90103-7
6.
DingW, TangD, JiangH, Influence of isothermal bainite transformation time on microstructure and mechanical properties of Hot-Dip Galvanized TRIP Steel. J Mater Eng Perform. 2011;20:997–1002. doi: 10.1007/s11665-010-9714-1
7.
TolouiM, MilitzerM.Phase field modeling of the simultaneous formation of bainite and ferrite in TRIP steel. Acta Mater. 2018;144:786–800. doi: 10.1016/j.actamat.2017.11.047
8.
BellhouseEM, McDermidJR.Effect of continuous galvanizing heat treatments on the microstructure and mechanical properties of high Al-low Si transformation induced plasticity steels. Metall Mater Trans A Phys Metall Mater Sci.2010;41:1460–1473. doi: 10.1007/s11661-010-0185-7
9.
LiuH, LiF, ShiW, Challenges in hot-dip galvanizing of high strength dual phase steel: Surface selective oxidation and mechanical property degradation. Surf Coatings Technol. 2012;206:3428–3436. doi: 10.1016/j.surfcoat.2012.02.001
10.
DingW, TangD, JiangH, Mechanical properties of continuously annealled Si-free P-containing TRIP steel. Acta Metall Sin. 2011;47:1022–1025.
11.
Jimenez-MeleroE, van DijkNH, ZhaoL, The effect of aluminium and phosphorus on the stability of individual austenite grains in TRIP steels. Acta Mater. 2009;57:533–543. doi: 10.1016/j.actamat.2008.09.040
12.
BarbéL, VerbekenK, WettinckE.Effect of the addition of P on the mechanical properties of low alloyed TRIP steels. ISIJ Int. 2006;46:1251–1257. doi: 10.2355/isijinternational.46.1251
13.
DingW, TangD, JiangH, Influence of martensite on mechanical properties of hot-dip galvanized trip steel. Acta Metall Sin. 2010;46:595–599. doi: 10.3724/SP.J.1037.2009.00773
14.
SugimotoK, MisuM, KobayashiM, Effects of second phase morphology on retained austenite morphology and tensile properties in a trip-aided dual-phase steel sheet. ISIJ Int. 1993;33:775–782. doi: 10.2355/isijinternational.33.775
15.
SherifMY, MateoCG, SourmailT, Stability of retained austenite in TRIP-assisted steels. Mater Sci Technol. 2004;20:319–322. doi: 10.1179/026708304225011180
16.
SugimotoK, KandaA, KikuchiR, Ductility and formability of newly developed high strength low alloy TRIP-aided sheet steels with annealed martensite matrix. ISIJ Int. 2002;42:910–915. doi: 10.2355/isijinternational.42.910
17.
JiangHT, DingW, TangD, Mechanical property and microstructural characterization of C-Mn-Al-Si Hot Dip Galvanizing TRIP Steel. J Iron Steel Res Int. 2012;19:29–36. doi: 10.1016/S1006-706X(12)60136-8
18.
DingW, GongZH, WangBF, Microstructure and mechanical properties of TRIP steel with annealed martensite. J Iron Steel Res Int. 2014;21:527–531. doi: 10.1016/S1006-706X(14)60082-0
19.
SugimotoK, HojoT, SrivastavaA.An overview of fatigue strength of case-hardening TRIP-Aided martensitic steels. Metals (Basel). 2018;8:355. doi: 10.3390/met8050355
20.
DingW, HedströmP, LiY.Heat treatment, microstructure and mechanical properties of a C-Mn-Al-P hot dip galvanizing TRIP steel. Mater Sci Eng A. 2016;674:151–157. doi: 10.1016/j.msea.2016.07.119
21.
CullityBD, StockSR.Elements of X-ray diffraction. 3rd ed. Upper Saddle River ( NJ): Prentice Hall; 2001.
22.
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. doi: 10.1016/j.actamat.2005.08.017
23.
ScottCP, DrilletJ.A study of the carbon distribution in retained austenite. Scripta Mater. 2007;56:489–492. doi: 10.1016/j.scriptamat.2006.11.033
24.
HanJ, LeeSJ, LeeCY, The size effect of initial martensite constituents on the microstructure and tensile properties of intercritically annealed Fe-9Mn-0.05C steel. Mater Sci Eng A. 2015;633:9–16. doi: 10.1016/j.msea.2015.02.075
25.
CaballeroFG, CapdevilaC, García de AndrésC.Kinetics and dilatometric behaviour of non-isothermal ferrite–austenite transformation. Mater Sci Technol. 2001;17:1114–1118. doi: 10.1179/026708301101511031
26.
KoistinenDP, MarburgerRE.A general equation prescribing the extent of the austenite-martensite transformation in pure iron-carbon alloys and plain carbon steels. Acta Metall. 1959;7:59–60. doi: 10.1016/0001-6160(59)90170-1
27.
AndrewsKW.Empirical formulae for the calculation of some transformation temperatures. J Iron Steel Inst. 1965;203:721–727.
28.
LiuC, ZhaoZ, NorthwoodDO, A new empirical formula for the calculation of MS temperatures in pure iron and super-low carbon alloy steels. J Mater Process Technol. 2001;113:556–562. doi: 10.1016/S0924-0136(01)00625-2
29.
SpeichGR, DemarestVA, MillerRL.Formation of austenite during intercritical annealing of dual-phase steels. Metall Trans A. 1981;12:1419–1428. doi: 10.1007/BF02643686
30.
GilmourJB, PurdyGR, KirkaldyJS.Thermodynamics controlling the proeutectoid ferrite transformations in Fe-C-Mn alloys. Metall Trans.1972;3:1455–1464. doi: 10.1007/BF02643033
31.
MukherjeeM, SinghSB, MohantyON.Neural network analysis of strain induced transformation behaviour of retained austenite in TRIP-aided steels. Mater Sci Eng A. 2006;434:237–245. doi: 10.1016/j.msea.2006.06.076
32.
JacquesPJ, FurneÂmontQ, MertensA, On the sources of work hardening in multiphase steels assisted by transformation-induced plasticity. Philos Mag A. 2001;81:1789–1813. doi: 10.1080/01418610108216637
33.
JacquesPJ, GiraultE, MertensA, The developments of cold-rolled TRIP-assisted multiphase steels. Al-alloyed TRIP-assisted multiphase steels. ISIJ Int. 2001;41:1068–1074. doi: 10.2355/isijinternational.41.1068
34.
SalehMH, PriestnerR.Retained austenite in dual-phase silicon steels and its effect on mechanical properties. J Mater Process Technol. 2001;113:587–593. doi: 10.1016/S0924-0136(01)00638-0
35.
EnnisBL, Jimenez-meleroE, AtzemaEH, Metastable austenite driven work-hardening behaviour in a TRIP-assisted dual phase steel. Int J Plast. 2017;88:126–139. doi: 10.1016/j.ijplas.2016.10.005
36.
HanHN, LeeCG, OhC, A model for deformation behavior and mechanically induced martensitic transformation of metastable austenitic steel. Acta Mater. 2004;52:5203–5214. doi: 10.1016/j.actamat.2004.07.031
