Effects of H content on the tensile properties and fracture behavior of SA508-III steel

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.

Section: Introductionmentioning

confidence: 99%

Hot Deformation Behavior and Microstructural Evolution of SA508‐IV Steel

Dai

Yang

2018

“…The trapping-detrapping kinetics in the McNabb-Foster model is described by the following equation: [167,168] ∂θ T ∂t ¼ k trap ð1 À θ T Þθ L À k detrap θ T (7) where θ L ¼ c L n L and θ T ¼ c T n T are the fraction of occupation for lattice and trapped hydrogen, respectively; k trap and k detrap are the rate constants for the trapping and detrapping process, respectively; and n is the total number of trapping sites. For lattice hydrogen, n L can be estimated by the number of solvent atoms in the material.…”

Section: Hydrogen Diffusionmentioning

confidence: 99%

“…[2][3][4][5] Accordingly, it has become a dilemma that advanced highstrength steels (AHSSs), originally designed to enhance safety levels, may suffer from a severe HE risk. [6][7][8] Typical examples that reveal high HE susceptibility can be found in quenching and partitioning steels and medium Mn steels with ultimate tensile strength (UTS) of more than 1000 MPa. [9][10][11][12] In recent years, ultrahigh-strength presshardened steels (PHSs) have been widely adopted in the automotive industry to build safety components, such as A-/B-pillars and bumpers.…”

Section: Introductionmentioning

confidence: 99%

“…[ 2–5 ] Accordingly, it has become a dilemma that advanced high‐strength steels (AHSSs), originally designed to enhance safety levels, may suffer from a severe HE risk. [ 6–8 ] Typical examples that reveal high HE susceptibility can be found in quenching and partitioning steels and medium Mn steels with ultimate tensile strength (UTS) of more than 1000 MPa. [ 9–12 ]…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hydrogen Embrittlement Evaluation and Prediction in Press‐Hardened Steels

Cao

Wang

Ngiam

et al. 2023

The application of press-hardened steels (PHSs) in automotive body-in-white components using the hot-stamping technique is growing thanks to its impressive strength and formability. Unfortunately, hydrogen embrittlement (HE), an issue that generally exists in high-strength steels, impedes the PHSs rising application trend by causing catastrophic mechanical property degradation. Thus, detailed evaluation and prediction of HE risk throughout PHSs manufacture and service condition are necessary. This study highlights techniques to characterize the hydrogen content and distribution, techniques to evaluate HE susceptibility, and potential models to simulate the in-service performance of PHS. The survey of existing studies has revealed the gaps between laboratory measurement and industry application, including but not limited to 1) the accelerated experiment-induced discrepancies against real-life applications, 2) a selection of the appropriate HE indicators, 3) an accurate risk prediction model, and 4) efficient feedback to the industry based on both experimental and simulated results. Based on the review, future studies are expected to establish a conclusive HE evaluation standard for PHS.

Recrystallization Behavior of Computationally Optimized Low‐Alloy Steel at Various Temperatures and Strain Rates

Abdullah,

Ahmad,

Rajendren

et al. 2024

The dynamic recrystallization (DRX) behavior of SA508‐III steel, a critical material for reactor pressure vessels (RPVs) normally treated by hot forging, is thoroughly examined in this article. In the investigation, elevated temperatures and the coarsening of metallic phases and carbides are revealed to contribute to the degradation of the steel's strength–toughness relationship. Utilizing computational thermodynamics, the stability of secondary phases, including carbides and brittle inclusions, is simulated to enable precise phase equilibrium calculations and accurate prediction of key mechanical properties such as yield strength, tensile strength, and hardness. These simulations facilitated targeted modifications to the alloy composition to enhance the steel's strength and hardenability under high‐temperature, high‐pressure conditions. In this study, alloy composition and processing parameters within the CALculation of PHAse Diagram framework, utilizing the ThermoCalc and JMatPro software packages, are optimized. In the microstructural investigations conducted under various isothermal deformation conditions (1173–1473 K) and strain rates (0.001–1 s−1), it is demonstrated that DRX mechanisms led to varied grain size developments, with a critical strain rate identified at 0.01 s−1 during high‐temperature deformations. In these findings, significant insights are provided into optimizing the mechanical performance of SA508‐III steel for RPV applications.