Incompatible effects of B and B + Nb additions and inclusions' characteristics on the microstructures and mechanical properties of low-carbon steels

Ali, Mohammed; Nyo, Tun Tun; Kaijalainen, Antti; Javaheri, Vahid; Tervo, Henri; Hannula, Jaakko; Somani, Mahesh C.; Kömi, Jukka

doi:10.1016/j.msea.2021.141453

Cited by 18 publications

(13 citation statements)

References 51 publications

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“…When boron segregation proceeds during austenite conditioning, additionally supported by a strong flux of vacancies towards the austenite boundaries, it is possible that no diffusible boron is left for covering the new austenite grain boundaries generated by dynamic recrystallization. Earlier investigations on the current and other boron-alloyed steels [2,[6][7][8] revealed that the hardenability effect related to boron is weakened when applying substantial strain immediately before quenching. In CCT diagrams reported in the previous works, the ferrite and bainite phase fields are then shifted towards shorter times and higher transformation temperatures under direct quenching conditions.…”

Section: Discussionmentioning

confidence: 95%

“…austenite grain boundaries generated by dynamic recrystallization. Earlier investigati on the current and other boron-alloyed steels [2,[6][7][8] revealed that the hardenability ef related to boron is weakened when applying substantial strain immediately be quenching. In CCT diagrams reported in the previous works, the ferrite and bainite ph fields are then shifted towards shorter times and higher transformation temperatures der direct quenching conditions.…”

Section: Discussionmentioning

confidence: 99%

“…This event produces a fraction of very fine equiaxed austenite grains. It has been shown that the application of large deformation strain at low austenite temperature and the presence of dynamically recrystallized austenite compromises the hardenability effect related to boron microalloying [2,[5][6][7][8]. The hardenability related to molybdenum alloying, however, appears to be much more robust under the same processing conditions.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Dynamic Recrystallization on Microstructural Evolution in B Steels Microalloyed with Nb and/or Mo

et al. 2022

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The dynamic recrystallization behavior of ultra-high strength boron-microalloyed steels optionally alloyed with niobium and molybdenum is analyzed in this paper. Multipass torsion tests were performed to simulate plate rolling conditions followed by direct quenching. The influence of alloy composition on the transformed microstructure was evaluated by means of EBSD, thereby characterizing the morphology of the austenite grain morphology after roughing and finishing passes. The results indicated that for Nb-microalloyed steel, partial dynamic recrystallization occurred and resulted in local clusters of fine-sized equiaxed grains dispersed within the pancaked austenitic structure. A recrystallized austenite fraction appeared and transformed into softer phase constituents after direct quenching. The addition of Mo was shown to be an effective means of suppressing dynamic recrystallization. This effect of molybdenum in addition to its established hardenability effects hence safeguards the formation of fully martensitic microstructures, particularly in direct quenching processes. Additionally, the circumstances initiating dynamic recrystallization were studied in more detail, and the interference of the various alloying elements with the observed phenomena and the potential consequences of dynamic recrystallization before quenching are discussed.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Dynamic Recrystallization on Microstructural Evolution in B Steels Microalloyed with Nb and/or Mo

et al. 2022

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“…In this case, Ti forms the more stable TiN instead of BN, ensuring that boron remains in solid solution. Ali et al [10] studied the potential factors that affect the B hardenability in low carbon alloyed steels, concluding that the formation of coarse precipitates of M 23 (B,C) 6 in AGBs led to the deterioration of toughness and affected the hardenability negatively.…”

Section: Propertiesmentioning

confidence: 99%

Synergism between B and Nb improves fire resistance in microalloyed steels

Ferreira¹,

Carvalho²,

Ariza-Echeverri³

et al. 2022

Preprint

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The development of new fire-resistant steels represents a challenge in materials science and engineering of utmost importance. Alloying elements such as Nb and Mo are generally used to improve the strength at both room-and high-temperatures due to, for example, the formation of precipitates and harder microconstituents. In this study we show alternatively that the addition of small amounts of boron in Nb-microalloyed steels may play a crucial role in maintaining the mechanical properties at high temperatures. The 66 % yield-strength criteria for fire resistance is achieved at ≈ 574 °C for a boron steel, whereas without boron this value reaches ≈ 460 °C, a remarkable boron-induced mechanical strengthening enhancement. DFT calculations show that boron additions can lower the vacancy formation energy when compared to pure ferrite and, for Nb-B steels, there is a further 24 % reduction, suggesting that the boron-niobium combination acts as an effective pinning-based strengthening agent.

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“…Na condição deformada, há também um maior aparecimento de fases como perlita e bainita para uma mesma taxa de resfriamento em relação à condição não deformada [78]. Em outro estudo, Ali et al [112] verificaram algo similar a Isasti et al [78], onde a deformação prévia favoreceu o aparecimento de fases como a bainita granular, a perlita e a ferrita poligonal por conta de alto número de sítios de nucleação e da falta de átomos em impedir o movimento das subestruturas de discordâncias formadas.…”

Section: Microestruturas E Diagrama Cctunclassified

Transformações de fase, microestruturas, e propriedades mecânicas de um aço resistente ao incêndio.

Gomes¹

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Agradeço à quem eu mais amo: minha mãe Maria Helena, ao meu pai Silvio (in memoriam), ao meu irmão André, e à minha família, e que sempre fizeram de tudo para priorizar minha educação, meu caráter, e minha pessoa.Agradeço ao meu orientador Professor Dr. Hélio Goldenstein pelo extremo carinho, apoio, confiança, cordialidade, simpatia, oportunidade e por ter me guiado nesse início dessa jornada da vida acadêmica.Ao Professor Dr. André Paulo Tschiptschin pelo cordial suporte, ajuda, e por oferecer a oportunidade de conhecer, crescer, discutir e trabalhar com os melhores.Ao meu coorientador, Dr. Julian Escobar David Atehortua pelas conversas, críticas, amizade, compreensão, aprendizado, e por acreditar em mim. Sem a sua ajuda este trabalho não seria o mesmo.Ao Mestre Felipe Moreno pela forte amizade e companheirismo durante o projeto. Ao Dr. Edwan Anderson Ariza Echeverri pelas frutíferas discussões e pela constante injeção de motivação, melhorando-me como pessoa. Ao Professor Dr. Julián Arnaldo Ávila Diaz por acompanhar, ajudar, apoiar e criticar quando necessário.Aos amigos e amigas da pós-graduação do PMT-USP e do Laboratório de Transformação de Fases (LTF) pelo ensino, ajuda, amizade, discussões e por propiciarem um ambiente incrível de se conviver. À República Masmorra pela amizade.Aos colegas do IPT, em especial a Dra. Ana Paola Villalva e ao Dr. Mario Boccalini Jr., por acompanharem, e estarem sempre presentes nas reuniões, tornando-as mais leves e produtivas.

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Incompatible effects of B and B + Nb additions and inclusions' characteristics on the microstructures and mechanical properties of low-carbon steels

Cited by 18 publications

References 51 publications

Effect of Dynamic Recrystallization on Microstructural Evolution in B Steels Microalloyed with Nb and/or Mo

Effect of Dynamic Recrystallization on Microstructural Evolution in B Steels Microalloyed with Nb and/or Mo

Synergism between B and Nb improves fire resistance in microalloyed steels

Transformações de fase, microestruturas, e propriedades mecânicas de um aço resistente ao incêndio.

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