Microstructure and mechanical behaviors of GPa-grade TRIP steels enabled by hot-rolling processes

Chen, Shih-Che; Wang, Yuan-Tsung; Lin, Yu‐Chen; Huang, Ching‐Yuan; Yang, Jue; Yen, Hung‐Wei

doi:10.1016/j.msea.2019.06.015

Cited by 25 publications

(12 citation statements)

References 45 publications

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“…Fourth, the presence of M/A films on the boundaries of the elongated micrograins can act as additional barriers for dislocation motion [49]. Although the austenite becomes unstable during mechanical loading (which may cause reduction in toughness), good ductility can be maintained via the transformation induced plasticity (TRIP) effect [57][58][59]. However, the exact deformation behavior of the RA/M-A films during the compression test performed in the current study is still not clear.…”

Section: Implication For Strengthening Mechanismsmentioning

confidence: 88%

Effect of cooling rate on the microstructure and mechanical properties of a low-carbon low-alloyed steel

Wang

Cao

et al. 2021

J Mater Sci

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Heavy plate steels with bainitic microstructures are widely used in industry due to their good combination of strength and toughness. However, obtaining optimal mechanical properties is often challenging due to the complex bainitic microstructures and multiple phase constitutions caused by different cooling rates through the plate thickness. Here, both conventional and advanced microstructural characterization techniques which bridge the meso- and atomic-scales were applied to investigate how microstructure/mechanical property-relationships of a low-carbon low-alloyed steel are affected by phase transformations during continuous cooling. Mechanical tests show that the yield strength increases monotonically when cooling rates increase up to 90 K/s. The present study shows that this is associated with a decrease in the volume fraction of polygonal ferrite (PF) and a refinement of the substructure of degenerated upper bainite (DUB). The fine DUB substructures feature C-rich retained austenite/martensite-austenite (RA/M-A) constitutes which decorate the elongated micrograin boundaries in ferrite. A further increase in strength is observed when needle-shaped cementite precipitates form during water quenching within elongated micrograins. Pure martensite islands on the elongated micrograin boundaries lead to a decreased ductility. The implications for thick section plate processing are discussed based on the findings of the present work.

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Section: Implication For Strengthening Mechanismsmentioning

confidence: 88%

Effect of cooling rate on the microstructure and mechanical properties of a low-carbon low-alloyed steel

Wang

Cao

et al. 2021

J Mater Sci

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show abstract

“…The entire curves can be divided into three stages which are the working hardening stage, thermally activated softening stage, and steady‐state stage, reflecting a result of competition between work hardening and dynamic softening. [ 21,22 ] In the initial deformation stage, the flow stress increases sharply (almost linear growth) with the augment of deformation degree. During this period, dislocation pile‐up and tangling dominate the deformation process.…”

Section: Resultsmentioning

confidence: 99%

Comparison Study of Hot Deformation Behavior and Microstructure Evolution of Rack Steels with and without Segregation

Wang

Kan

et al. 2022

steel research int.

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In order to compare the hot deformation behavior and microstructure evolution of the rack steels with and without segregation, hot compression tests are carried out in the temperature range of 1173–1423 K and the strain rate range of 0.01–10 s−1 on a DIL805A/D quenching and deformation dilatometer. The flow stress, constitutive relation, processing map, and microstructure characterization are investigated. The results show that the flow stress increases with the increase of strain rate and the decrease of deformation temperature. The calculated activation energy (Q) and stress exponent (n) for the segregated samples are 395.245 kJ mol−1 and 6.046, which are higher than segregated samples, showing 376.815 kJ mol−1 and 5.930. The processing maps show that the workability of the nonsegregated steel is significantly more excellent than segregated steel. The segregated steel shows a higher kernel average misorientation angle and local strain. Complete dynamic recrystallization occurs at a high strain rate, and high deformation temperature can refine the grains.

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“…The GND represents the distortion of crystal lattice which can be introduced by volume expansion and lattice rotation during transformation and deformation. [ 25,33 ] Tu et al [ 34 ] pointed that the formation and annihilation of GND could affect the distribution of stress and strain during tensile process, resulting in affecting the work hardening behavior. The phase maps and GND distribution maps are shown in Figure 11 .…”

Section: Discussionmentioning

confidence: 99%

Significance of Retained Austenite Stability on Yield Point Elongation Phenomenon in a Hot‐Rolled and Intercritically Annealed Medium‐Mn Steel

Dong

et al. 2022

steel research int.

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The effect of retained austenite stability on yield point elongation (YPE) phenomenon in a hot‐rolled and intercritically annealed medium‐Mn steel is elucidated here. Furthermore, the influencing factors of austenite reversion are studied. The results indicate that the shear phase transition is suppressed by the strain hardening of prior austenite grain introduced by low‐temperature rolling, resulting in refined martensite laths with high dislocation density. The nucleation and growth of intercritical austenite are accelerated by high‐density dislocation substructures. Different characteristics of retained austenite (RA) are obtained through tailoring the rolling temperature and austenite reversion transformation (ART) process. YPE phenomenon is a result of the equilibrium between work hardening (via martensitic transformation and dislocation multiplication) and softening (by stress relaxation and dislocation glide). In the initial deformation stage, large amounts of geometrically necessary dislocations (GND) are “stored” in the RA with higher stability, and the local stress can be effectively relaxed and transferred, leading to the occurrence of YPE. The optimum properties are obtained in R760‐A630‐0.3h samples with a combination of yield strength of 918 MPa, tensile strength of 1019 MPa, and total elongation of 25.3%, which is mainly attributed to the finer ferrite matrix and sustained transformation‐induced plasticity effect.

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Microstructure and mechanical behaviors of GPa-grade TRIP steels enabled by hot-rolling processes

Cited by 25 publications

References 45 publications

Effect of cooling rate on the microstructure and mechanical properties of a low-carbon low-alloyed steel

Effect of cooling rate on the microstructure and mechanical properties of a low-carbon low-alloyed steel

Comparison Study of Hot Deformation Behavior and Microstructure Evolution of Rack Steels with and without Segregation

Significance of Retained Austenite Stability on Yield Point Elongation Phenomenon in a Hot‐Rolled and Intercritically Annealed Medium‐Mn Steel

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