Non-equilibrium intergranular segregation in ultra low carbon steel

Zhang, Zaoli; Lin, Qingyun; Yu, Zong-Sen

doi:10.1179/026708300101507695

Cited by 18 publications

(18 citation statements)

References 14 publications

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“…The present work has shown using a cooling rate of 60 o C/min that the presence of B in addition to Ti gives better ductility for the temperature range 700~900 o C. From previous work on boron containing TWIP steels [141,175,177] even better ductility would be expected if the cooling rate was slower, closer to 10 o C/min and such a secondary cooling rate may be needed to avoid transverse cracking.…”

Section: Discussionmentioning

confidence: 52%

“…Zhang et al [141] have shown that for the ultra-low C steel they examined, cooling from 1050 o C resulted in the maximum segregation occurring when the cooling rate was ~10 o C/min in accord with the work of Yamoto et al [175] and Chown and Cornish [177]. Hence, slower cooling rates of 10~15 o C/min would be recommended to give better ductility [171] as this allows more B to segregate to the boundaries as well as coarsening the TiN precipitates.…”

Section: Discussionmentioning

confidence: 99%

“…Zhang et al [141] have also found that the B segregation is very dependent on cooling rate. Using Auger electron microscopy they showed that B segregates to austenite grain boundaries in low C, Nb containing steels (0.046%Nb, 0.0007%B) and the segregation is non-equilibrium.…”

Section: Hot Ductility Of "Re-heated" To 1250 O C Steelsmentioning

confidence: 91%

“…When their steel was quenched from 1200 o C and held at 900 o C for various times it was found that a B peak occurred first followed by P and then S after a long time. Under non equilibrium conditions the excess vacancies produced on quenching, combine with the impurities and the complex diffuses to the grain boundary where dissociation occurs and the boundary region enriches in impurities [141]. However, at the same time there is also the reverse diffusion of impurities away from the boundary through normal diffusion which reduces the concentration at the boundaries.…”

Section: Hot Ductility Of "Re-heated" To 1250 O C Steelsmentioning

confidence: 99%

“…Perrot-Simonetta and Kobylanski have suggested that B prevents S segregating to the boundaries [170]. Cooling rate is also important and average cooling rates in the range 10 to 100 o C/min are needed; the lower the cooling rate in this range, the more effective B is in improving ductility [141,175,177].…”

Section: Introductionmentioning

confidence: 99%

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Hot ductility of TWIP steels

Kang

Tuling

Banerjee

et al. 2011

Materials Science and Technology

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The hot ductility of twin induced plasticity (TWIP), 0·6 wt-C steels containing 18–22 wt-Mn with N levels in the range 0·005–0·023 wt- and the Al additions either low (<0·05 wt-) or high (1·5 wt-) has been examined. Little change in ductility occurred in the temperature range 1100–650°C as the structure was always fully austenitic. Ductility was generally poor (<40), reduction of area values, the best ductility at the higher Al level being given by the steel with the lowest N and S levels. Because the steel is fully austenitic, the ductility is solely dependent on that for unrecrystallised austenite. Therefore, to avoid transverse cracking the volume of second phase particles should be kept to a minimum, i.e. the N should be low to reduce the amount of AlN that can be precipitated out and the S level should be as low as possible to limit the amount of MnS inclusions. Metallographic and TEM studies were carried out and the poor ductility was found to be due to extensive precipitation of AlN at the austenite grain boundaries. Increasing the cooling rate from the melting point to the test temperature from 60 to 180°C min−1 or introducing an undercooling step both led to even worse ductility.

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Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Section: Hot Ductility Of "Re-heated" To 1250 O C Steelsmentioning

confidence: 91%

Section: Hot Ductility Of "Re-heated" To 1250 O C Steelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hot ductility of TWIP steels

Kang

Tuling

Banerjee

et al. 2011

Materials Science and Technology

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Theoretical progress in non-equilibrium grain-boundary segregation (II): Micro-mechanism of grain boundary anelastic relaxation and its analytical formula

Wang

Song

2009

Sci. China Ser. E-Technol. Sci.

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Finding the internal-friction peak of grain boundary anelastic relaxation was one of the important breakthroughs in the study of internal friction in the last century. But the micro-mechanism of grain boundary anelastic relaxations is still obscure. Based on the observations of the grain boundary segregation or depletion of solute induced by an applied stress, the following micro-mechanism was suggested: grain-boundaries will work as sources to emit vacancies when a compressive stress is exerted on them and as sinks to absorb vacancies when a tensile stress is exerted, inducing grainboundary depletion or segregation of solute, respectively. The equations of vacancy and solute concentrations at grain boundaries were established under the equilibrium of grain-boundary anelastic relaxation. With these the kinetic equations were established for grain boundary segregation and depletion during the grain boundary relaxation progress. grain boundary, segregation, anelastic relaxation, kineticsThe variation of micro-structure in materials induced by an applied stress has been an important study field in materials science and engineering. The slip, climb and interaction of dislocations under applied stresses induce the plastic deformation of materials, which are the main content in the research of mechanical properties. A great deal of engineering practice has confirmed that the degradation of properties, embrittlement, creep, fatigue and brittle fracture without any sign will occur in metallic materials during service to produce engineering accidents. Metal usually serves under an applied stress which is lower than its yield limit and at the same time the degradation of its mechanical properties occurs. Therefore, what kind of micro-structure variations will appear for polycrystalline materials under an elastic stress? How will these variations influence the mechanical properties and the performance in service? These have been the most urgent and vexing challenges to the present materials scientists and engineers. In the 1940s, Chinese scientist Ke found the internal friction peak of grain boundary anelastic relaxation, which was one of the important achievements in the field of elastic stress to induce the variations of micro-structure in the last century. But the micro-mechanism of grain boundary anelastic relaxation was still obscure [1] , and the situation gave rise to the argument whether or not the internal friction peak found by Ke was relative to the grain boundary anelastic relaxation [2] . Recently, we found that the main micro-structure variation of polycrystalline under an elastic stress was absorbing or emitting vacancies to produce grain boundary segregation or depletion of solutes during grain boundary anelastic re

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Graphical representation for isothermal kinetics of non-equilibrium grain-boundary segregation

Wang

Song

et al. 2011

Materials Characterization

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Non-equilibrium intergranular segregation in ultra low carbon steel

Cited by 18 publications

References 14 publications

Hot ductility of TWIP steels

Hot ductility of TWIP steels

Theoretical progress in non-equilibrium grain-boundary segregation (II): Micro-mechanism of grain boundary anelastic relaxation and its analytical formula

Graphical representation for isothermal kinetics of non-equilibrium grain-boundary segregation

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