Cleavage Fracture Initiation at M–A Constituents in Intercritically Coarse-Grained Heat-Affected Zone of a HSLA Steel

Mohseni, Peyman; Solberg, Jan Ketil; Karlsen, Morten; Akselsen, Odd M.; O̸stby, Erling

doi:10.1007/s11661-013-2110-3

Cited by 91 publications

(47 citation statements)

References 12 publications

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“…Therefore, the recrystallized grains were high carbon twin martensite and retained austenite, which had also been proved in some researches. [24][25][26] The twin substructure belonged to transformation inducing twinning due to supercooled austenite transformation to martensite at low temperature. Figure 5 shows the kernel average misorientation (KAM) and strain contouring map with different magnification in order to reflect the strain concentration in recrystallized grains and prior austenite grains.…”

Section: Substructure Study Of Recrystallization By T-ebsdmentioning

confidence: 99%

Microstructure and Micro Strain in the CGHAZ of 2.25Cr-1.6W Steel after Intercritical Heat Treatment

2017

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Section: Substructure Study Of Recrystallization By T-ebsdmentioning

confidence: 99%

Microstructure and Micro Strain in the CGHAZ of 2.25Cr-1.6W Steel after Intercritical Heat Treatment

2017

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“…[1,2] However, welding of pipeline steels continues to be a cause for concern because of the presence of local brittle zone (LBZ) in the heat-affected zone (HAZ). [3,4] During deformation, cleavage fracture can nucleate at the LBZ [5,6] and subsequently propagate from LBZ. In the HAZ, there are several sub-zones including coarse-grained (CG) HAZ, fine-grained (FG) HAZ, intercritically reheated coarse-grained (ICCG) HAZ and so on.…”

Section: Thermo-mechanically Processed X80-x100mentioning

confidence: 99%

“…It is generally accepted that CGHAZ and ICCGHAZ are the most detrimental regions from the point of view of toughness and cleavage fracture may occur in the two regions during impact. [3,[5][6][7][8] Thus, there is a need to understand the correlation of structure-property-cleavage fracture mechanism in the HAZ, especially in CGHAZ and ICCGHAZ.…”

Section: Thermo-mechanically Processed X80-x100mentioning

confidence: 99%

“…In regard to nucleation, at least three possible mechanisms have been suggested and include: (a) crack initiation at grain boundaries caused by pile-up of dislocations, [9,10] (b) cracking of inclusions, large second phase particle or martensiteÀaustenite (MÀA) constituent present within the grains or along the grain boundaries, [5][6][7]11] , and (c) decohesion of inclusions/MÀA from matrix. [6][7][8] Cleavage fracture occurs when (1) the maximum principal stress (r yy ) close to the crack tip exceeds fracture stress (r f ) over a characteristic distance, [12] or (2) the microcracks, nucleated ahead of the main crack tip because of high stress field, [13] interconnect with each other. [14] During propagation, there is competition between the microcracks formed at the crack front.…”

Section: Thermo-mechanically Processed X80-x100mentioning

confidence: 99%

“…This kind of MÀA constituent can promote nucleation of brittle fracture either through cracking or debonding from the matrix. [5][6][7] B. Charpy Impact Toughness and Fracture Surface Characterization Charpy impact energy of X100 base plate, samples with notch I, II, and weld metal at À20°C is presented in Table III. The average Charpy impact energy of notch I was 183 J and is~3.6 times that of notch II (51 J).…”

Section: A Microstructurementioning

confidence: 99%

See 2 more Smart Citations

Structure–Property–Fracture Mechanism Correlation in Heat-Affected Zone of X100 Ferrite−Bainite Pipeline Steel

Subramanian

et al. 2015

Metallurgical and Materials Transactions E

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Structural performance of a weld joint primarily depends on the microstructural characteristics of heat-affected zone (HAZ). In this regard, the HAZ in X100 ferriteÀbainite pipeline steel was studied by separating the HAZ into intercritically reheated coarse-grained (ICCG) HAZ containing and non-containing regions. These two regions were individually evaluated for Charpy impact toughness and characterized by electron back-scattered diffraction (EBSD). Low toughness of~50 J was obtained when the notch of impact specimen encountered ICCGHAZ and high toughness of~180 J when the notch did not contain ICCGHAZ. Fracture surface was 60 pct brittle in the absence of ICCGHAZ, and 95 pct brittle (excluding shear lip) in the presence of ICCGHAZ in the impact tested samples. The underlying reason is the microstructure of ICCGHAZ consisted of granular bainite and upper bainite with necklace-type martensiteÀaustenite (MÀA) constituent along grain boundaries. The presence of necklace-type M-A constituent notably increases the susceptibility of cleavage microcrack nucleation. ICCGHAZ was found to be both the initiation site of the whole fracture and cleavage facet initiation site during brittle fracture propagation stage. Furthermore, the study of secondary microcracks beneath CGHAZ and ICCGHAZ through EBSD suggested that the fracture mechanism changes from nucleation-controlled in CGHAZ to propagation-controlled in ICCGHAZ because of the presence of necklace-type M-A constituent in ICCGHAZ. Both fracture mechanisms contribute to the poor toughness of the sample contained ICCGHAZ.

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Phase Transformation and Precipitation Mechanism of Nb Microalloyed Bainite–Martensite Offshore Platform Steel at Different Cooling Rates

Xiong

Song

et al. 2019

steel research int.

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The phase transformation and precipitation mechanism of Nb microalloyed offshore platform steel during continuous cooling are studied by the thermal expansion method and transmission electron microscopy. The results show that a large amount of NbC is precipitated in the investigated steel during phase transformation and is classified into three types according to its size: Type I (>100 nm) is randomly generated in the austenitization stage; type II (20–100 nm) is precipitated by stress induction during thermal deformation; and type III (≈10 nm) is formed by the combination of segregated C and Nb during the cooling process after the formation of bainitic ferrite matrix. In addition, herein, a model of phase transition and precipitation behavior at different cooling rates is designed. At a low cooling rate (0.5 °C s−1), the microstructure consists of a granular structure formed by diffusion and granular bainite formed by shearing, which is a diffusion phase transformation. At a medium cooling rate (3 °C s−1), the orientation relationship of ferrite and austenite is [001]α//[011]γ and (110)α//(−1−11)γ, which is semidiffusion and a half‐shear mechanism. At a high cooling rate (15 °C s−1), there are a large number of intertwined dislocations in martensite, which is a shear mechanism.

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Cleavage Fracture Initiation at M–A Constituents in Intercritically Coarse-Grained Heat-Affected Zone of a HSLA Steel

Cited by 91 publications

References 12 publications

Microstructure and Micro Strain in the CGHAZ of 2.25Cr-1.6W Steel after Intercritical Heat Treatment

Microstructure and Micro Strain in the CGHAZ of 2.25Cr-1.6W Steel after Intercritical Heat Treatment

Structure–Property–Fracture Mechanism Correlation in Heat-Affected Zone of X100 Ferrite−Bainite Pipeline Steel

Phase Transformation and Precipitation Mechanism of Nb Microalloyed Bainite–Martensite Offshore Platform Steel at Different Cooling Rates

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