Stability of precipitates under electropulsing in 316L stainless steel

Lu, W.J.; Zhang, X. F.; Qin, Rongshan

doi:10.1179/1743284714y.0000000743

Cited by 50 publications

(22 citation statements)

References 15 publications

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“…The original free energy sequence is hence changed due to 15 the extra electric current free energy. It has been proved that electric current helps to dissolve low conductive phase embedded in a high conductive matrix [27][28]38]. The observed reduction of -carbides is alongside with this prediction.…”

Section: Discussionsupporting

confidence: 58%

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Influence of κ-carbide interface structure on the formability of lightweight steels

Qin

2016

Materials & Design

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Abstractκ-carbide () in high aluminium (Al) steels is grown from austenite () via + or α+ ( represents ferrite), and is a lamellar structure. This work demonstrates that the formability of high Al lightweight steels is affected by the lattice misfit and interface shape between  and matrix. The cold workability can be improved by either to change the steel chemical constitution or to implement an electro-thermo-mechanical process. For ferrite-matrix-based high Al steel, electric-current promotes the spheroidization and refinement of  structure and reduces volume fraction of  phase. This retards the crack nucleation and propagation, and hence improves the materials formability. The observation is caused by a direct effect of electric-current rather than side effects.

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Section: Discussionsupporting

confidence: 58%

“…Electropulsing has also been implemented to alternate the volume fraction of precipitate [27][28]. The annealed Fe-26Mn-9Al-0.75C samples were subjected to an electric current pulse with peak current density of 1.92×10 9 Am -2 .…”

Section: Electropulsing Microstructure To Improve the Formabilitymentioning

confidence: 99%

Influence of κ-carbide interface structure on the formability of lightweight steels

Qin

2016

Materials & Design

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“…The total bulk free energy of the steel includes two terms which are the chemical free energy of the bulk phases ( ), and the free energy associated with the passing electric current pulses ( ). The free energy change due to electric current pulse can be determined by [11,13,14]: are the current densities at position r and , respectively. μ is the magnetic permeability.…”

Section: Resultsmentioning

confidence: 99%

Effect of electric current pulses on the microstructure and niobium carbide precipitates in a ferritic-pearlitic steel at an elevated temperature

Rahnama

Qin

2015

J. Mater. Res.

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Niobium is an important alloying element in steels. In the present work an effort has been made to investigate the effect of electropulsing on the niobium carbide (NbC) at an elevated temperature (800 ºC). The results show that the electropulsing treatment can generate an evenly distributed NbC by decreasing the kinetics barriers for precipitation. It has been also found that a semi-transformed pearlite structure forms in such a way that the grains are oriented towards a direction parallel to that of the electric current flow. Furthermore, the electropulsed sample benefits from refined grain size. This is thought to be due to the electropulse-enhanced nucleation rate. Tensile testing has been carried out in order to compare the properties of electropulsed sample with that of without electropulsing. The results show that the sample with treatment has greater yield strength and ultimate tensile stress (UTS) while its elongation is only 1% less that of the unelectropulsed samples. The improved mechanical properties of the sample with pulsing are attributed to its finer grain sizes as well as the elimination of precipitation free zones (PFZs) caused by the electropulsing treatment.

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“…Thus, the process reduces the temperature at which recrystallisation, recovery or relaxation occurs, [10][11][12][13] but the phenomena are probably not associated with electromigration. 14 Although it is claimed qualitatively that the thermodynamic free energy of the system is changed by a quantity DG elec due to the application of current pulses in systems with mixtures of phases, 15 the evidence is incomplete. Proof would involve the substitution of DG elec into a routine phase diagram calculation package to show that yes, the equilibrium phase fractions are quantitatively altered as observed.…”

Section: H K D H Bhadeshiamentioning

confidence: 99%

The Electrical Processing of Materials

Bhadeshia¹

2015

Materials Science and Technology

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High frequency pulses of electrical current have long been known to induce dramatic changes in the structure and properties of materials, 1 including for example, the healing of internal cracks in microseconds 2,3 and electrically induced plasticity as an aid to shape forming. [4][5][6] If the temperature rise associated with the pulsing is sufficient, then the dislocation density can be affected even if the pulse duration is just a few millionths of a second. 7 In a recent editorial, I commented on the promise of the method, which thus far has not had any major exploitation, and on the need for a theoretical framework that is quantitatively predictive. 8 To explore these ideas further, a critical assessment was commissioned, 9 the conclusions from which can be paraphrased as follows:1. it is possible that the method may replace thermomechanical processing because the capital requirement is smaller, at least on the laboratory scale that has been explored thus far. 2. That there is no single case where theory has been applied quantitatively. 3. That speculation regarding the contribution of electrical energy to the free energy of transformation has yet to be justified [to the same extent that stress and magnetic fields have been incorporated into phase diagram calculations]. 4. That in phase mixtures, the variation in electrical resistivity or magnetic properties of the individual phases may determine the structural response to electropulsing. There evidently is a lot to be done, so the next step in the assessment of the field became obvious, to initiate a compilation of papers on the subject, with all those active in the field according to the knowledge databases, invited to contribute.

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Stability of precipitates under electropulsing in 316L stainless steel

Cited by 50 publications

References 15 publications

Influence of κ-carbide interface structure on the formability of lightweight steels

Influence of κ-carbide interface structure on the formability of lightweight steels

Effect of electric current pulses on the microstructure and niobium carbide precipitates in a ferritic-pearlitic steel at an elevated temperature

The Electrical Processing of Materials

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