Constitutive equation and dynamic recrystallization behavior of as-cast 254SMO super-austenitic stainless steel

Han, Ying; Wu, Hongxing; Zhang, Wei; Zou, Dening; Liu, Guiwu; Qiao, Guanjun

doi:10.1016/j.matdes.2014.12.049

Cited by 90 publications

(39 citation statements)

References 46 publications

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“…In addition, there is competitive relationship between work hardening and dynamic softening (Figure ). Dislocations rapidly accumulate and multiplication results in the remarkable increase of the work hardening, which is dominant mechanism during the initial deformation stage . While the dislocations occur annihilation and regular rearrangement with the increase of strain.…”

Section: Resultsmentioning

confidence: 99%

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Hot Deformation Behavior and Microstructural Evolution of SA508‐IV Steel

Dai

Yang

2018

steel research int.

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The hot deformation behavior and microstructural evolution of SA508-ІV steel are studied through hot compressive tests in the temperature range of 950-1250 C, and in the strain rate range of 0.001-1 s À1 . The hot deformation activation energy and the stress exponent are calculated to be 328.73 KJ mol À1 and 3.29 by the regression analysis of sine hyperbolic function. On this basis, the constitutive Equations are developed. Moreover, the relationship between work hardening and dynamic softening is explained, and a two-stage constitutive model is established to predict the flow stress of SA508-ІV steel. The predicted and experimental values show a good consistency. Based on the conventional dynamic recrystallization kinetics model, the volume fraction of the dynamic recrystallization is also estimated, and the results show that the maximum fraction is close to 100% under the higher temperature and lower strain rate. Furthermore, the microstructural evolutions at different deformation conditions are also analyzed, and the DRX grain size has an exponential increase with increasing deformation temperature and decreasing strain rate.

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Section: Resultsmentioning

confidence: 99%

“…The DRX grain size is merely controlled by Z parameter, the formula has been recognized by many researchers:

d_{drx} = C Z^{- m}

where d drx (μm) is the grain size of DRX, and C , m are the material constants. The values of C and m are derived from the linear regression of Figure a.…”

Section: Resultsmentioning

confidence: 99%

Hot Deformation Behavior and Microstructural Evolution of SA508‐IV Steel

Dai

Yang

2018

steel research int.

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“…The flow stress increases with the increase of strain rate and the decrease of deformation temperature. The peak stress and corresponding strain decline with the decrease of strain rate and the increase of deformation temperature, indicate that pronounced work hardening can easily occur at lower strain rates and higher temperatures [13]. Higher temperature could provide lager driving force for the dynamic restoration and thus accelerate the grain boundary migration and dislocation movement.…”

Section: Methodsmentioning

confidence: 99%

Microstructure Evolution and Strain-Dependent Constitutive Modeling to Predict the Flow Behavior of 20Cr–24Ni–6Mo Super-Austenitic Stainless Steel During Hot Deformation

Hao

Liu

2017

Acta Metall. Sin. (Engl. Lett.)

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Hot compression tests were carried out with specimens of 20Cr-24Ni-6Mo super-austenitic stainless steel at strain rate from 0.01 to 10 s-1 in the temperature range from 950 to 1150°C, and flow behavior was analyzed. Microstructure analysis indicated that dynamic recrystallization (DRX) behavior was more sensitive to the temperature than strain rate, and full DRX was obtained when the specimen deformed at 1150°C. When the temperature reduced to 1050°C, full DRX was completed at the highest strain rate 10 s-1 rather than at the lowest strain rate 0.01 s-1 because the adiabatic heating was pronounced at higher strain rate. In addition, flow behavior reflected in flow curves was inconsistent with the actual microstructural evolution during hot deformation, especially at higher strain rates and lower temperatures. Therefore, flow curves were revised in consideration of the effects of adiabatic heating and friction during hot deformation. The results showed that adiabatic heating became greater with the increase of strain level, strain rate and the decrease of temperature, while the frictional effect cannot be neglected at high strain level. Moreover, based on the revised flow curves, strain-dependent constitutive modeling was developed and verified by comparing the predicted data with the experimental data and the modified data. The result suggested that the developed constitutive modeling can more adequately predict the flow behavior reflected by corrected flow curves than that reflected by experimental flow curves, even though some difference existed at 950°C and 0.01 s-1. The main reason was that plenty of precipitates generated at this deformation condition and affected the DRX behavior and deformation behavior, eventually resulted in dramatic increase of deformation resistance.

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“…These values are much higher than those for self-diffusion barrier energy in γ-iron (Q  280 kJ· mol −1 ). Compared with other reported Mo-containing SASS values, such as Fe-20Cr-25Ni-4.5Mo (Qmax  443 kJ mol −1 ), Fe-25Cr-22Ni-7Mo (Qmax  469 kJ· mol −1 ), Fe-16Cr-25Ni-6Mo (Qmax  484 kJ· mol −1 ), Fe-20Cr-18Ni-6Mo (Qmax  577 kJ· mol −1 ), and Fe-25Cr-30Ni-3Mo (Qmax  656 kJ· mol −1 ) [13,14,16,18,36], the activation barrier in the steel under observation in this study is significantly high, and the hot deformation is rather difficult. In particular, the variations in the Q values presents a rising trend with increases in strain and begins to decline until the true strain is reached at 0.75.…”

Section: Verification Of the Developed Constitutive Model With Strainmentioning

confidence: 99%

Constitutive Relationship Modeling and Characterization of Flow Behavior under Hot Working for Fe–Cr–Ni–W–Cu–Co Super-Austenitic Stainless Steel

Pan

Chen

et al. 2015

Metals

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The hot deformation behavior of a Fe-22Cr-25Ni-3.5W-3Cu-1.5Co super-austenitic stainless steel was investigated using isothermal compression tests with a wide range of temperatures (1173-1373 K) and strain rates (0.1-10 s −1 ). The results showed that all the flow curves gradually turned to balanced stress state without notable peak stress characteristics during the entire deformation, which indicated that the dynamic recovery behavior played a main restoration mechanism in the steel. Modeling constitutive equations relating to the temperature, strain rate and flow stress were proposed to determine the materials constants and activation energy necessary for deformation. In order to give the precise predicted values of the flow behavior, the influence of strain was identified using polynomial functions. The relationship of flow stress, temperature and strain rate was represented by the Zener-Hollomon parameter including the Arrhenius term. The predicted results validated that the developed constitutive equations can describe high temperature flow behavior well. Furthermore, a modified Zener-Hollomon parameter map of the studied steel was developed to clarify the restoration mechanism based on the constitutive modeling data and microstructural observation. OPEN ACCESSMetals 2015, 5 1718

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Constitutive equation and dynamic recrystallization behavior of as-cast 254SMO super-austenitic stainless steel

Cited by 90 publications

References 46 publications

Hot Deformation Behavior and Microstructural Evolution of SA508‐IV Steel

Hot Deformation Behavior and Microstructural Evolution of SA508‐IV Steel

Microstructure Evolution and Strain-Dependent Constitutive Modeling to Predict the Flow Behavior of 20Cr–24Ni–6Mo Super-Austenitic Stainless Steel During Hot Deformation

Constitutive Relationship Modeling and Characterization of Flow Behavior under Hot Working for Fe–Cr–Ni–W–Cu–Co Super-Austenitic Stainless Steel

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