Wenwen Song

Wenwen Song
University of Kassel · Institut für Werkstofftechnik (IfW)

Professor

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66
Publications
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1,286
Citations

Publications

Publications (66)
Preprint
Full-text available
The present work investigates the atomic interactions among Cu, Al, and Ni elements in bcc-iron matrix, focusing on the formation mechanism of nano-sized core-shell Cu precipitates. Using a combination of atom probe tomography (APT), density functional theory (DFT) cal-culations, and molecular dynamics (MD) simulations, the study provides insights...
Article
Full-text available
The effect of the scarcely reported F phase on hydrogen-assisted cracking in nickel-based Alloy 725 was thoroughly studied by combining tensile tests, advanced characterization, and density functional theory (DFT) calculations. The results show grain boundary precipitate F phase promotes intergranular fracture in a hydrogen environment. DFT calcula...
Article
Full-text available
In this paper, the high strength and lightweight Al-Cu-Li alloy (AA2099) is considered in as-built and preheated conditions (440 • C, 460 • C, 480 • C, 500 • C, and 520 • C). The purpose of this study is to investigate the influence of laser powder bed fusion (LPBF) in situ preheating on precipitation microstructure, mechanical and corrosive proper...
Article
Herein, the Fe–5Mn–2Al–0.1C (wt%) and micro‐alloyed Fe–5Mn–2Al–0.1C–0.1Nb–0.2V (wt%) medium Mn steels are processed by a novel flash‐austenite‐reverse‐transformation (ART) annealing. The core–shell Mn‐gradient in austenite is observed and compositionally characterized at near‐atomic scale by using atom probe tomography. Compared with the convention...
Article
Full-text available
Herein, the effect of shortening the intercritical annealing (IA) time in a two‐step process “intercritical annealing and tempering (IAT)” on the microstructure and the mechanical properties of medium‐manganese steel (MMnS) made of Fe–0.05C–7Mn–1.5Cu–1.5Ni–1.5Al–1.5Si–0.5Mo (wt%) and containing copper‐rich (CRP) and Ni(Al/Mn) precipitates is invest...
Article
The nanoscale Cu precipitation exhibits considerable potential for enhancing strength and cyclic hardening potential in steels. In the present work, Cu-alloyed ferritic steels with different C contents (X0.5: 0.005 wt.%, X21: 0.21 wt.%) were investigated to systematically manifest the influences of C contents on the microstructural evolution, the p...
Presentation
Increasing the recycling rate is the most efficient way to improve the carbon foot print of steel making. Remelting scrap in the electric arc furnace (EAF) requires only 20% of the energy that is needed in the primary iron-ore-reduction route. However, the cleanliness of the EAF process is often not sufficient to fulfil the demanding specifications...
Chapter
Metallic materials, particularly advanced steels with superior properties, are used extensively in almost every aspect of our lives, including transportation, construction, communication, energy, household appliances, and medical instruments, making it one of the most important materials in human society. Global challenges, such as climate change,...
Article
Full-text available
In this paper, we report the influence of cooling processes on the yielding behavior of a medium Mn steel (MMS) with triplex microstructure, i.e. austenite (γ), ferrite (α) and as-quenched martensite (α'). After the intercritical annealing (IA) at both 725 ℃ and 750 ℃, the steel was subjected to the two cooling processes, i.e. air cooling (AC) and...
Article
Carbon containing high-manganese steels are susceptible to strain aging, which influences the mechanical properties during and after deformation. To understand the strain aging behavior of austenitic Fe-22Mn-1.3Al-0.3C high-manganese steel, dynamic as well as static strain aging were examined. Dynamic strain aging, occurring during deformation, was...
Article
Full-text available
Breaking the strength-ductility paradox of very-low (≤0.05 wt.%)-C medium (3–12 wt.%)-Mn steels (MMnS) has been a hard-wired topic, since in these steels multi-step heat treatments are usually required to obtain austenite for improved ductility and precipitates for higher strength. In this study, a compact two-step heat treatment comprising short (...
Article
Full-text available
Developing medium-Mn steels (MMnS) demands a better understanding of the microstructure evolution during thermo-mechanical treatments (TMTs). This study demonstrates the relationship among processing, microstructure, and mechanical properties of a warm-rolled medium-Mn steel (MMnS) containing 1.5 wt. % Cu and 1.5 wt. % Ni. After short-time warm rol...
Article
Full-text available
Evaluation of hydrogen effect on the fatigue crack growth behavior of medium-Mn steels via in-situ hydrogen plasma charging in an environmental scanning electron microscope, Abstract Fatigue crack growth (FCG) tests were conducted on a medium-Mn steel annealed at two intercritical annealing temperatures, resulting in different austenite (γ) to ferr...
Article
Full-text available
Austenitic high manganese steels exhibit outstanding mechanical properties, such as high energy absorption, owing to various deformation-mechanisms such as dislocation slip, twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP). Here, we show a novel thermomechanical treatment to manufacture a high manganese steel Fe–18Mn-...
Article
In this study, the austenite transformation in a cold-rolled medium-Mn steel (MMnS; 7 wt.% Mn) was adjusted by inter-critical annealing (IA) at 680 °C (above the Ac1 temperature) and by partition annealing (PA) at 650 °C (below the Ac1 temperature). The deformation behavior associated with the microstructural evolution, and crystallographic changes...
Article
Full-text available
Medium-Mn steels have attracted immense attention for automotive applications owing to their outstanding combination of high strength and superior ductility. This steel class is generally characterized by an ultrafine-grained duplex microstructure consisting of ferrite and a large amount of austenite. Such a unique microstructure is processed by in...
Article
Understanding the effects of microstructural defects, which can have a high impact on service life, is of great importance in the design of cyclically loaded components. For this, the size of the defect as well as the material's ability to counteract microstructural defects have to be considered. In this study, the defect tolerance of differently h...
Article
Full-text available
A novel Cr-alloyed medium-Mn steel was designed and manufactured for the hot forming application in automobile. Compared to the typical press hardening steel (PHS) grade of 22MnB5, it possesses more excellent mechanical combination and enormously reduced oxidization after press hardening. The synchrotron-based high-energy X-ray diffraction experime...
Presentation
As many other industries relies the forging industries on high strength steels especially for automotive application. Martensitic quench and tempering alloys, like 42CrMo4 are commonly used, as these materials show a good balance of strength and impact toughness. Currently, these classic design properties are getting replaced by the cyclic material...
Article
The combination of different phase constituents to realize a mechanical composite effect for superior strength-ductility synergy has become an important strategy in microstructure design in advanced high-strength steels. Introducing multiple phases in the microstructure essentially produces a large number of phase boundaries. Such hetero-interfaces...
Article
In this study electron diffraction coupled with aberration-corrected STEM is used to unequivocally image, identify and confirm the structure producing the double diffracted spots seen in all electron diffraction patterns in twinned high carbon steels. The experimental and simulated data unequivocally show that regions comprising: (i) overlaps betwe...
Article
Full-text available
Plasma nitriding is successfully employed in treating AlxCoCrFeNi high-entropy alloys (HEAs) with finely-divided Al content (i.e., x values in molar ratio, x = 0.1- 0.8) to develop wear-resistant structural materials. Nitridation greatly removes the Al from the matrix that completely deplete the Ni-Al enriched phase, forming nanoscaled nitrides (Al...
Article
Full-text available
Ti and its alloys have a variety of applications in aerospace industry and medical implants. The formation of hydride has been used in biomedical areas and can significantly influence the mechanical performance of materials. In this work, we investigate the orientation dependence of hydride precipitation in commercially pure titanium via interrupte...
Preprint
Nowadays, most structural integrity concepts rely on simplified isotropic ma-terial data that are used within continuum mechanics modeling approaches. In contrast, modern casting and forming processes yield complex microstruc-tures coming along with pronounced gradients in the material's properties in various length scales. By means of additive man...
Article
Precipitation behavior and austenite stability of the warm-rolled medium-Mn steels with different Nb/Mo additions annealed at different temperatures were investigated. The Nb or Nb–Mo additions decrease the volume fraction of retained austenite, but increase its mechanical stability. The Mo addition to the Nb-bearing steels can lead to a higher den...
Article
Full-text available
The ultrafine-grained (UFG) duplex microstructure of medium-Mn steel consists of a considerable amount of austenite and ferrite/martensite, achieving an extraordinary balance of mechanical properties and alloying cost. In the present work, two heat treatment routes were performed on a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C (wt.%) to achieve...
Article
Ultrafine austenite-ferrite duplex medium Mn steels often show a discontinuous yielding phenomenon, which is not commonly observed in other composite-like multiphase materials. The underlying dislocation-based mechanisms are not understood. Here we show that medium Mn steels with an austenite matrix (austenite fraction ∼65 vol.%) can exhibit pronou...
Article
Ultrafine austenite-ferrite duplex medium Mn steels often show a discontinuous yielding phenomenon, which is not commonly observed in other composite-like multiphase materials. The underlying dislocation-based mechanisms are not understood. Here we show that medium Mn steels with an austenite matrix (austenite fraction ~65 vol%) can exhibit pronoun...
Article
Medium-Mn steel is the newly developed steel acting as a promising candidate of the 3rd-generation advanced high strength steels. In the present study, the effect of hydrogen on the mechanical behavior and martensite transformation process in a duplex medium-Mn steel is investigated by in-situ nanoindentation test. The mechanical response of indivi...
Article
In-situ annealing experiments using synchrotron diffraction depict the separation of {100}-superlattice peaks ascribed to C-enrichment of pre-existing, C-lean Ĺ12-ordered structures into C-rich κ-carbides of alike crystal structure during heating of a high-Al lightweight steel. The peak separation is the first experimental in-situ investigation of...
Conference Paper
The formation of coherent κ-carbide precipitates is known to significantly increase the yield strength of high-Mn steels. Understanding their impact on the mechanical performance, however, requires simulation of their thermodynamic stability, chemical composition and interfaces with the adjacent matrix. These factors influence the interaction with...
Conference Paper
Full-text available
The medium-Mn steel possesses ultrafine-grained (UFG) duplex microstructure consisting of ferrite and a large amount of metastable austenite. The metastable austenite in UFG duplex microstructure is obtained by austenite reversion during intercritical annealing. The study of austenite reversion kinetics is of great importance for the heat treatment...
Conference Paper
Full-text available
With the development of high-strength steels, hydrogen embrittlement has been recognized as a severe problem in applications. It leads to hydrogen-induced premature failure of materials and unexpected catastrophe of structural components. To understand the mechanisms of hydrogen embrittlement and manage this issue are significantly important for th...
Conference Paper
Die Bemessung technischer Strukturbauteile beruht auch heute noch in vie-len Fällen auf der Annahme isotroper Materialeigenschaften, die in kontinu-umsmechanische Modelle einfließen. Demgegenüber stehen komplex aufge-baute Werkstoffe, deren Mikrostruktur durch moderne Ur-und Umformver-fahren eine ausgeprägte Ortsabhängigkeit in verschiedenen Längen...
Article
In the present work, isothermal lower bainitic transformation with nano‐sized cementite (θ) precipitation is simulated by means of multiphase‐field approach. In order to simulate the very fine cementite, ultra‐small grid spacing, that is, 2 nm, is applied. A faceted anisotropy model is coupled in the simulation of both bainitic ferrite (αB) and cem...
Article
The recrystallization behavior of a high-Mn high-Al lightweight steel (Fe-28.4Mn-8.3Al-1.27 C (wt%)) with 50% cold rolling deformation is investigated at the annealing temperature of 800 °C, 900 °C and 1000 °C. The detailed microstructure evolution is characterized by optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter...
Article
Full-text available
Medium-Mn steels are characterized by ultrafine-grained (UFG) duplex microstructure consisting of ferrite and a large amount of retained austenite. Intercritical annealing is of great importance to achieving the UFG duplex microstructure and adjusting amount as well as stability of retained austenite. In the present work, the influence of intercrit...
Article
Full-text available
The localized deformation in the high-Mn austenitic Fe-18Mn-0.6C (wt %) steel manifests itself as serrations in the stress–strain curves and Portevin–Le Chatelier (PLC) bands characterized by digital image correlation (DIC) analysis in uniaxial tensile tests. The serrated flow is correlated with the nucleation, propagation and dying away of PLC ban...
Article
The bake hardening treatment shows great potential for increasing the yield strength of steel components for automotive applications. This study investigates the effects of bake hardening on the yield strength and ductility of an austenitic high-Mn steel. In order to identify a promising process window, the prestrain, the bake hardening temperature...
Article
Full-text available
The formation of Mn–C short-range ordering (SRO) has a great influence on the mechanical properties of high-Mn steels. In the present work, the formation of Mn–C SRO during recrystallization of an X60Mn18 steel was investigated by means of a combined study employing small angle neutron scattering (SANS) and ab initio ground-state energy calculation...
Article
Full-text available
The quantitative characterization of the microstructure evolution in high-Mn steel during deformation is of great importance to understanding its strain-hardening behavior. In the current study, in situ high-energy synchrotron X-ray diffraction was employed to characterize the microstructure evolution in a Fe-17Mn-1.5Al-0.3C steel during a tensile...
Article
Martensite decay in bearing steels manifested as dark etching regions (DERs) under rolling contact fatigue (RCF) is modelled. The proposed model is established based on a dislocation-assisted carbon migration mechanism. The proposed model is capable of predicting the progress of DER formation and the corresponding mechanical property evolution with...
Article
In the present work, a quaternary CoCrFeNi high entropy alloy (HEA) is investigated by means of high energy synchrotron X-ray diffraction (SYXRD) and small angle neutron scattering (SANS). At the as-forged state, the microstructure of CoCrFeNi HEA is pure austenite. The as-cast dendritic structure has been eliminated by the hot forging at about 110...
Article
Full-text available
Al containing intermetallic phases have been evaluated in various bcc and fcc steels. Attractive application options have been derived for hot working tools steels with respect to a reduction of resource critical alloying elements and in cold formable steels by the combined density reduction and strength increase.
Poster
The quantitative characterization of the deformation microstructure evolution in high-Mn austenitic TRIP/TWIP steel is of great importance for the understanding of its strain hardening behavior. Stacking fault energy (SFE) exhibits the decisive role to control the strain hardening behavior in high-Mn austenitic steels. In the present work, the in-s...
Poster
In steel research, the deep understanding of the structure-property relationship requires powerful tools to characterize nano-scale phenomena. Small angle neutron scattering (SANS) makes possible to characterize nano-sized particles content of sample volume in mm3 range by means of size, size distribution and volume fraction. Synchrotron XRD (SYXRD...
Chapter
In the design of high strength steels, bainite structures gain importance because of their excellent balance of strength and toughness. However, bainite still remains the least understood austenite decomposition reaction. Following the philosophy of Integrated Computational Materials Engineering (ICME), we combine various simulation and advanced ch...
Article
In the present work, a combined approach of ab initio theoretical calculations and in situ synchrotron X-ray diffraction is used to investigate the κ-phase formation in Fe-Mn-Al-C austenitic steels. In order to understand the driving forces for short- and long-range ordering in the Fe-Mn-Al-C steels, a fully systematic approach is used for DFT calc...
Chapter
In the design of high strength steels, bainite structures gain importance because of their excellent balance of strength and toughness. However, bainite still remains the least understood austenite decomposition reaction. Following the philosophy of Integrated Computational Materials Engineering (ICME), we combine various simulation and advanced ch...
Chapter
This contribution reports the results of the collaborative research unit SFB 761 “Steel — ab initio”, a cooperative project between RWTH Aachen University and the Max-Planck-Institute for Iron Research in Düsseldorf (MPIE) financed by the German Research Foundation (DFG). For the first time, in a structural measure it is exploited how ab initio app...
Article
Austenitic high-Mn steels with Mn contents between approximately 15 and 30 wt% gain much interest because of their excellent mechanical properties and the option for adjusting strain hardening behavior due to different deformation mechanisms. 2D and 3D composition-dependent stacking fault energy (SFE) maps indicate the effect of chemical compositio...
Article
Atom probe analysis of partitioning in steel ################################# We report on the characterization of high carbon bearing steel 100Cr6 using electron microscopy and atom probe tomography in combination with multi-component diffusion simulations. Scanning electron micrographs show that around 14 vol pct spheroidized carbides are formed...
Article
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Article
Carbide precipitation during upper and lower bainite formation in high-carbon bearing steel 100Cr6 is characterized using transmission electron microscopy and atom probe tomography. The results reveal that both epsilon and theta carbides precipitate in lower bainite isothermally held at 260 °C and only theta precipitates form in upper bainite isoth...
Article
Carbide precipitation during upper and lower bainite formation in high-carbon bearing steel 100Cr6 is characterized using transmission electron microscopy and atom probe tomography. The results reveal that both e and h carbides precipitate in lower bainite isother-mally held at 260 °C and only h precipitates form in upper bainite isothermally held...
Article
Carbide precipitation during upper and lower bainite formation in high-carbon bearing steel 100Cr6 is characterized using transmission electron microscopy and atom probe tomography. The results reveal that both e and h carbides precipitate in lower bainite isother-mally held at 260 °C and only h precipitates form in upper bainite isothermally held...
Article
We report on the characterization of high carbon bearing steel 100Cr6 using electron micro-scopy and atom probe tomography in combination with multi-component diffusion simulations. Scanning electron micrographs show that around 14 vol pct spheroidized carbides are formed during soft annealing and only 3 vol pct remain after dissolution into the au...
Article
Bainitic structure is of considerable importance in the design of high strength steels for application in fatigue loading condition. In order to better understand the mechanisms of bainitic structure formation and to model its microstructure evolution, 2D phase-field simulations were performed coupled with CALPHAD method. In the present work, high...

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