Nonequilibrium grain-boundary cosegregation of nitrogen and chromium in NiCrMoV steel

The research progress of non-equilibrium grain-boundary segregation theories in the last 20 years is reviewed. Based on studies by the present authors, the critical time of non-equilibrium segregation and its impact on the development of non-equilibrium segregation theories are described. Quasi-thermodynamics and kinetics for thermal non-equilibrium grain boundary segregation are detailed along with a non-equilibrium grain boundary cosegregation model. The experimental validation of the theories and their application to the reversible temper embrittlement of steels and the intermediate temperature brittleness in metals and alloys are also addressed.grain-boundary, segregation, embrittlement

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“…Zheng and Xu [56] calculated the binding energies of Cr and N with a vacancy and their interaction energy in Fe. Using eq.…”

Section: Non-equilibrium Grain Boundary Cosegregation (Ngcs)mentioning

confidence: 99%

Theoretical progress in non-equilibrium grain-boundary segregation (I): Thermally induced non-equilibrium grain-boundary segregation and intergranular embrittlement

Wang

Song

2009

Sci. China Ser. E-Technol. Sci.

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“…In 1987, Xu22 formulated the effect in terms of equation (3). The effect of TNGS temperature difference was experimentally confirmed in different alloy systems 47,49,5861…”

Section: Theoretical Framework Of Non-equilibrium Grain Boundary Segr...mentioning

confidence: 81%

“…The effect of TNGS temperature difference was experimentally confirmed in different alloy systems. 47,49,[58][59][60][61] 4 The relationship between maximum TNGS concentration C m and the temperature difference T o 2T, calculated from equation (3) Fig. 6 as a function of aging temperature.…”

Section: Effect Of Temperature Differencementioning

confidence: 99%

“…1 23 ), S in Cu doped ferrite alloy, 36 Ni, Sb and Ti in a low carbon NiCr steels, 37 P in 12Cr1MoV steel, 38 P, S and B in ultralow carbon steel, 39 Mg, S and P in a Ni base alloy, [40][41][42] P in an Ni-Cr steel 43 and 304L stainless steel, 44,45 Ni and Sn as well as N and Cr in 2?6NiCrMoV steel. 46,47 When the holding time at a particular temperature after quenching was longer than the critical time, the TNGS concentration of impurities decreases, and thus, the intergranular embrittlement induced by the impurities also decreases on prolonging the holding time at a particular temperature. This is a ductility healing effect and is validated experimentally in the next section.…”

Section: Critical Timementioning

confidence: 99%

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Unified mechanism of intergranular embrittlement based on non-equilibrium grain boundary segregation

Liu

Wang

et al. 2013

International Materials Reviews

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The review is aimed at presenting a unified approach in understanding the mechanism of nonequilibrium grain boundary segregation, which can satisfactorily describe the three types of intergranular embrittlement, namely, reverse temper embrittlement of steels, intergranular corrosion embrittlement of stainless steels and intermediate temperature embrittlement of metals and alloys. The review starts with a broad perspective of non-equilibrium grain boundary segregation, including thermally induced non-equilibrium grain boundary segregation and stress induced non-equilibrium grain-boundary segregation. Next, it focuses on the recent progress made in the non-equilibrium grain boundary segregation, including (1) critical time, (2) segregation peak temperature, (3) segregation peak temperature movement for thermally induced and stress induced non-equilibrium grain boundary segregation, and (4) the effect of temperature difference on thermally-induced non-equilibrium grain boundary segregation. Next, the attention is focused on the grain boundary coverage of elements and intergranular embrittlement phenomena. Three types of intergranular embrittlement is analysed in terms of (1) the ductility healing effect induced by the critical time, (2) embrittlement peak or ductility trough induced by the segregation peak temperature, (3) embrittlement peak or ductility trough movement induced by the segregation peak temperature movement and (4) widening and deepening of ductility trough induced by differences in temperature. These experimental phenomena concerning the three types of intergranular embrittlement are consistent with the models of thermally induced and stress induced non-equilibrium grain boundary segregations of impurities, instead of precipitation or equilibrium grain boundary segregation. Towards the end, we visit the subject of grain boundary segregation and associated embrittlement process from the viewpoint of fracture resistance and briefly discuss different perspectives that are of practical significance. List of symbolsA constant b the Burger's vector B Norton coefficient C b (t c ) grain boundary concentration at critical time C b(s50) equilibrium concentration of solute at the grain boundaries C g concentration of solute within the grains C v s~0 ð Þ equilibrium vacancy concentration at grain boundaries C v s~s ð Þ grain boundary vacancy concentration induced by the tensile stress D b the diffusivity D c diffusion coefficients for complexes under or in absence of applied tensile stress D i diffusion coefficients for solute atoms under or in absence of applied tensile stress E the elastic or Young's modulus -E the embrittlement sensitivity in K/at-% of solute at the grain boundary E b formation energy of vacancy solute atom complex International Materials Reviews 2013 VOL 58 NO 5263 E f vacancy formation energy E gb the elastic or Young's modulus of grain boundary region F v the formation energy of a vacancy in the boundary region H Z intergranular Auger peak to peak height of an element normalised with the ...

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“…[27] In addition, bulk concentration of soluble V is reduced by strong affinity to C and formation of vanadium carbides. [28][29][30][31] Based on AES spectra, GB segregation of P was calculated by the approach described in ref. [25,26] At least 20 GBs were measured to obtain the average.…”

Section: Experiments and Resultsmentioning

confidence: 99%

Investigations on Grain Boundary Segregation Energy of Phosphorus in 12Cr1MoV Steel Under Elastic Stress

Zheng

Lejček

et al. 2015

Adv Eng Mater

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Grain boundary (GB) concentration of P in 12Cr1MoV steel after aging for 15 h under elastic stress of 30 MPa is found to be nearly equal to its initial thermal equilibrium level, which confirms that elastic stress affects thermal equilibrium segregation slightly. By the model and formulation between elastic stress and segregation Gibbs energy, the effect of elastic stress on GB segregation thermodynamics of P is calculated to be slight. The consistency between experiment and calculation gives direct evidence to the validity of the model and formulation.

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Nonequilibrium grain-boundary cosegregation of nitrogen and chromium in NiCrMoV steel

Cited by 16 publications

References 37 publications

Theoretical progress in non-equilibrium grain-boundary segregation (I): Thermally induced non-equilibrium grain-boundary segregation and intergranular embrittlement

Theoretical progress in non-equilibrium grain-boundary segregation (I): Thermally induced non-equilibrium grain-boundary segregation and intergranular embrittlement

Unified mechanism of intergranular embrittlement based on non-equilibrium grain boundary segregation

Investigations on Grain Boundary Segregation Energy of Phosphorus in 12Cr1MoV Steel Under Elastic Stress

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