Pearlite formation via martensite

Li, Songjie; He, Mengyuan; Hu, Guanjie; Tian, Yun; Wang, Chengduo; Jing, Ben; Ping, Dehai

doi:10.1016/j.compositesb.2022.109859

Cited by 11 publications

(4 citation statements)

References 27 publications

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“…This strength level improvement can be attributed to the tempered martensite microstructure. As generally documented [21][22][23], a tempered temperature has significant effects on quenched martensite. In the present work, tempering at 700 • C for the Q&T processing largely promoted the desolvation of supersaturated carbon atoms from the quenched martensite matrix, contributing to carbide formation in the tempered martensite and thus leading to the resulting precipitation strengthening.…”

Section: Tensile Properties and Ssc Evaluationmentioning

confidence: 73%

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment

Zhang,

Zhao,

Tian

et al. 2024

Materials

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Sulfide stress cracking (SSC) failure is a main concern for the pressure vessel steel Q345 used in harsh sour oil and gas environments containing hydrogen sulfide (H2S). Methods used to improve the strength of steel usually decrease their SSC resistance. In this work, a quenching and tempering (Q&T) processing method is proposed to provide higher strength combined with better SSC resistance for hot-rolled Q345 pressure vessel steel. Compared to the initial hot-rolled plates having a yield strength (YS) of ~372 MPa, the Q&T counterparts had a YS of ~463 MPa, achieving a remarkable improvement in the strength level. Meanwhile, there was a resulting SSC failure in the initial hot-rolled plates, which was not present in the Q&T counterparts. The SSC failure was not only determined by the strength. The carbon-rich zone, residual stress, and sensitive hardness in the banded structure largely determined the susceptibility to SSC failure. The mechanism of the property amelioration might be ascribed to microstructural modification by the Q&T processing. This work provides an approach to develop improved strength grades of SSC-resistant pressure vessel steels.

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Section: Tensile Properties and Ssc Evaluationmentioning

confidence: 73%

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment

Zhang,

Zhao,

Tian

et al. 2024

Materials

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“…In metals and alloys, a high density of twinning structure has been observed only in quenched high carbon martensite. 34,35 In the present simulation, a high density of twin structure should cause satellite peaks in conventional X-ray powder diffraction patterns. However, these satellite peaks have never been observed and discussed.…”

Section: Discussionmentioning

confidence: 85%

“…The ultrahigh density means that the twinned crystal thickness is extremely small about 1–2 nm in the present investigation. The body-centered cubic (BCC) {112}<111>-type twin structure will be considered simply because such a twinning structure possess the highest density. , Figure explains a theoretical situation about twinned crystals, which can produce extra peaks in X-ray powder diffraction. An ideal single crystal is shown in Figure a in which a representative atom is marked by a red dot.…”

Section: Discussionmentioning

confidence: 99%

Double Diffraction or ω-Fe Diffraction in Body-Centered Cubic {112}<111>-Type Twinned Martensite

Zhai

Zhang

et al. 2022

Crystal Growth & Design

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The martensitic substructure in steels plays a major role in understanding the nature of martensite transformation and improving mechanical properties. However, the substructure in the quenched martensite of carbon steel, particularly in high carbon martensite, has not been clarified yet. Local crystal structure in martensite has been characterized by means of transmission electron microscope (TEM). A specimen tilting experiment in TEM is a practical method to simply confirm that the electron diffraction spots are caused by either double diffraction effect or a second crystalline phase. By tilting the TEM specimen containing Fe–C twinned martensite structure, the so-called double diffraction spots of {112}<111>-type twin are still visible even after the diffraction spots from the twinned crystals become invisible. This experimental result is the direct evidence that the so-called twinning double diffraction spots come from a second crystalline phase (ω-phase), which is distributed in the body-centered cubic (BCC){112}<111>-type twinning boundary region. An ideal BCC {112}<111>-type twin is just a model, which has not been reported yet in any experiment.

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“…The presence of high-density BCC {112}⟨111⟩-type twinning structures in α-Fe can be clearly observed in fast-cooled martensite structures, particularly in medium-to high-carbon quenched martensite. − Moreover, carbon atoms obviously exist within twinned martensite, resulting in the formation of carbides upon tempering. , The assumption that twinned martensite consists only of an α-Fe {112}⟨111⟩-type twin structure fails to explain the presence of carbon atoms or carbides in tempered martensite. If carbon atoms exist within the crystal structure of α-Fe, then these carbon atoms are generally believed to cause a transformation from a BCC α-Fe structure to a BCT Fe structure, particularly in high-carbon steels, which contradicts the {112}⟨111⟩-type twinning structure of α-Fe.…”

Section: Introductionmentioning

confidence: 99%

HRTEM Investigations on the Substructures of the Quenched Pearlite and Martensite

Zhu,

Yue,

Zhou

et al. 2024

Crystal Growth & Design

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The substructures of pearlite and martensite in a water-quenched Fe-1.4C (wt %) binary alloy were investigated via optical microscopy, scanning electron microscopy and high-resolution transmission electron microscopy. In the carbide layers of the quenched pearlite lamellae, θ-Fe3C-type cementite particles and several novel carbides were observed. According to electron diffraction patterns, the crystal structure of twinned martensite could not be characterized as a body-centered tetragonal crystal structure, which is commonly assumed. Instead, the patterns suggested that the twinned martensite could be considered to have a body-centered cubic α-Fe {112}⟨111⟩-type twinning structure accompanied by a metastable ω-Fe phase (ultrafine particles) at the twinning boundaries. Furthermore, high-resolution lattice observations of twinned martensite substructures demonstrated that ω-Fe phase particles could exist independently in regions without twinning structures, indicating that they were not solely caused by overlap at twinning boundaries; thus, this prior assumption was challenged. The mechanism of the formation of new carbides in quenched pearlite and the presence of the ω-Fe phase in the regions without twinning could be reasonably explained by the autotempering or detwinning of the twinned martensite.

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Pearlite formation via martensite

Cited by 11 publications

References 27 publications

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment

Double Diffraction or ω-Fe Diffraction in Body-Centered Cubic {112}<111>-Type Twinned Martensite

HRTEM Investigations on the Substructures of the Quenched Pearlite and Martensite

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