Abstract
This study investigates the bainitic transformation kinetics of carbide-free bainitic steel with Si + Al and carbide-bearing bainitic steel without Si + Al, as well as the phase transformation and microstructure through in situ high-temperature laser scanning confocal microscopy. Results show that bainitic ferrite plates preferentially nucleate at the grain boundary. New plates nucleate on previously formed ones, including two dimensions which appear on a plane where a three-dimensional space of bainitic ferrite forms. Nucleation on the formed bainitic ferrite is faster than that at the grain boundary in some grains. The bainitic ferrite growth at the austenite grain boundary is longer and has a faster transformation rate. The bainitic ferrite growth on the formed bainitic ferrite plate is shorter and has a slower transformation rate. The location and number of nucleation sites influence the thickness of the bainitic ferrite. The higher the number of plates preferentially nucleating at the original austenite grain boundary, the greater the thickness of the bainitic ferrite.
Highlights
Bainite possesses the most colorful structure in steel, and numerous forms of bainite have been discovered
The morphological characteristics of bainite are closely associated with the transformation temperature and alloying component
Carbide-bearing bainite is characterized by the precipitation of carbide within or between bainitic ferrite plates
Summary
Bainite possesses the most colorful structure in steel, and numerous forms of bainite have been discovered. Bhadeshia and Caballero [5,6,7,8,9] explored the distribution of carbon and alloying elements in the bainitic ferrite phase and the retained austenite phase in bainitic steels through atom probe technology (APT), X-ray diffraction measurements, and transmission electron microscopy (TEM). CAasrbtihdee-btreaanrsinfogrmbaaitniiotne tobhpnp2rcbyaurlaacovncrutncelehsereefpesateowrhtdirMeefemhssst,UehesaonnraetGneeimtcoswGaatnethr8ht.bpehc3eAolhrpasnleceatroecmeectfo-tsovtdeirwnicadriomatlaicueslnraonesegcsnlto.neytsomuoTibffocoe0rtpnlherceotamsaeaesilutdmTiesetsudp0iepooaabeonnlccrafuaeapwiutrntohrvushiefetterveeibelcn(niaaaoiipcistustnkelhssaiteitohlhtsiyefoceflriwfotfnioeiewnpnetrret)mree,ireirnrtfineeasntdeFheccfriecaologgutnriniuyndmoterhiniestnssheg(1p(eerTbboeqtp0l,widuunsreicoaotsoulltco.ridaridfrrvaiTmcseuallih.uaenseent)Tsene.td)hcsnTe,iuinibohrstreianeewvtdisegebnaawrliasoutarniahrfiecdnosiatcc.warlfihAlalresscnrias,onlrspettictfhhtpeoaieenererl,csmaftFwueoirimcalrghaottmiuiteinooecreidhnnaesr ptehxoetienentffFsdieguecdunt ,rdoetfeh2rfeefdrosrihbffitoleeiwqrseustnoettrhlecoeadnrrgeebinlotauentridogcionynnsachtlaeilupninstbeseedidtswbiscyeaaeplalnpeddetihasterphslre.aecTlae0tmicveuenrtvtiemtr.aeTnahsnfeodTrtm0heaatnnioudnmTmb0eecrcuhorafvnneisusacmlreeoasntiiomthnielsaicrtu,ebsrvuinet itshecognrsaiidnebreodunbdaaseryd aonndthbeaiTni0ticcufrevreri.teF.oTrhcearnbuidmeb-bereaorfinngucblaeaintiioten, sciatrebsimdearpkreedcilpyivtaatriioens cboentwsuemeneGs a2 larger amount of carbon and results in a lower carbon content in residual austenite as compared to carbide-free bainite. The former bainitic transformation is complete and does not require further transformation time. The transformation content of carbide-free bainite reaches approximately 90% within a short time
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