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Control of strain Hardening Behavior in High-Mn Austenitic steels

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Acta Metallurgica sinica(English Letters) 2014年第3期27卷 546-556页

作者： Wenwen song Tobias Ingendahl Wolfgang bleck steel Institute RWTH Aachen University Intzestr.1 52072 AachenGermany

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 composition and temperature on sFE and consequently on the deformation mechanisms. Three steels with different chemical compositions and the same or different sFE are characterized in quasi-static tensile tests. The control parameters of strain hardening behavior in the high-Mn austenitic steels are described, and consequences for future developments are discussed.

关键词： High-Mn austenitic steels stacking fault energy strain hardening

semi-hot stamping as an Improved Process of Hot stamping

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Journal of Materials science & Technology 2011年第4期27卷 369-376页

作者： Malek Naderi Mostafa Ketabchi Mahmoud Abbasi Wolfgang bleck Department of Mining and Metallurgy Amirkabir University of Technology Department of Ferrous Metallurgy RWTH-Aachen University

Reducing the forming load, deletion of springback, increasing the formability of sheets as well as producing high strength parts are the main reasons to apply hot stamping process. Hot stamping process and 22MnB5 steels are the state of the art process and grades, respectively; however novel processes and steel grades are under considerations. In the current research, behavior of the steel grade MsW1200 blanks under semi and fully hot stamping processes was characterized. During semi-hot stamping process, the blank was firstly heated to a temperature of about 650℃ and then formed and quenched in the die assembly, simultaneously. Microstructure and mechanical properties of semi and fully hot stamped blanks were studied and the results were compared with those of normally water/air quenched blanks. The hot stamped blanks attained the strength values as high as water quenched blanks. The highest ductility and consequently, the best formability were achieved for the blank which had been semi-hot stamped. It was concluded that for the mentioned steel, semi-hot stamping process could be considered as an improved thermo-mechanical process which not only guaranteed a high formability, but also led to ultra high strength values.

关键词： semi-hot stamping Hot stamping MsW1200 steel Mechanical properties

Hydrogen effect on the mechanical behaviour and microstructural features of a Fe-Mn-C twinning induced plasticity steel

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 835-846页

作者： Xiaofei Guo stefan Zaefferer Fady Archie Wolfgang bleck steel Institute RWTH Aachen UniversityIntze-str.1Aachen 52072Germany Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straße 1Düsseldorf 40237Germany NLMK Europe Eutelis-Platz 2Ratingen 40878Germany

The influences of hydrogen on the mechanical properties and the fracture behaviour of Fe-22Mn-0.6C twinning induced plasticity steel have been investigated by slow strain rate tests and fractographic *** steel showed high susceptibility to hydrogen embrittlement,which led to 62.9%and 74.2%reduction in engineering strain with 3.1 and 14.4 ppm diffusive hydrogen,*** fracture surfaces revealed a transition from ductile to brittle dominated fracture modes with the rising hydrogen *** underlying deformation and fracture mechanisms were further exploited by examining the hydrogen effects on the dislocation substructure,stacking fault probability,and twinning behaviour in pre-strained slow strain rate test specimens and notched tensile specimens using coupled electron channelling contrast imaging and electron backscatter diffraction *** results reveal that the addition of hydrogen promotes planar dislocation structures,earlier nucleation of stacking faults,and deformation twinning within those grains which have tensile axis orientations close to//rolling direction and//rolling *** developed twin lamellae result in strain localization and micro-voids at grain boundaries and eventually lead to grain boundary decohesion.

关键词： twinning induced plasticity steel hydrogen mechanical behaviour dislocation twinning electron channelling contrast imaging

New Microalloyed steels for Forgings

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Journal of Iron and steel Research International 2011年第S1期18卷 104-111页

作者： Christoph Keul Wolfgang bleck Department of Ferrous Metallurgy RWTH Aachen UniversityGermany

Microalloyed steels for forging applications have been newly developed in order to increase strength and toughness properties which thereby give the possibility for light weight *** properties of these steels are set up by a controlled cooling directly from the forging heat without an additional heat *** aim can be achieved on the one hand by a further development of precipitation hardening ferritic pearlitic steels (AFP-steel) due to an extended use of microalloying elements (AFP-M steel) and on the other hand by microalloyed steels which employ a bainitic microstructure (HDB steel).To adjust the targeted microstructure the temperature control has to be assured down to approx.500℃ for the AFP-M steels and down to approx.300℃ for the HDB steels.

关键词： forgings bainite microalloying controlled cooling

Transarterial chemoembolization using degradable starch microspheres and iodized oil in the treatment of advanced hepatocellular carcinoma: evaluation of tumor response, toxicity, and survival

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Hepatobiliary & Pancreatic Diseases International 2007年第3期6卷 259-266页

作者： Timm D Kirchhoff joerg s.bleck Arne Dettmer Ajay Chavan Herbert Rosenthal sonja Merkesdal Bernd Frericks Lars Zender Nisar P Malek Tim F Greten stefan Kubicka Michael P Manns Michael Galanski Department of Diagnostic Radiology Hannover Medical school Germany Department of Gastroenterology Hepatology and Endocrinology Hannover Medical School Germany Department of Diagnostic and Interventional Radiology Klinikum Oldenburg Germany Division of Rheumatology Hannover Medical School Germany Department of Radiology and Nuclear Medicine Campus B.F-Charité-University Medicine Berlin Germany

BACKGROUND: In a multidisciplinary conference patients with advanced non-resectable hepatocellular carcinoma (HCC) were stratified according to their clinical status and tumor extent to different regional modalities or to best supportive care. The present study evaluated all patients who were stratified to repeated transarterial chemoembolization (TACE) from 1999 until 2003 in terms of tumor response, toxicity, and survival. A moderate embolizing approach was chosen using a combination of degradable starch microspheres (DsM) and iodized oil (Lipiodol) in order to combine anti-tumoral efficiency and low toxicity. METHODs: Fourty-seven patients were followed up prospectively. TACE treatment consisted of cisplatin (50 mg/m2), doxorubicin (50 mg/m2), 450-900 mg DsM, and 5-30 ml Lipiodol. DsM and Lipiodol were administered according to tumor vascularization. Patient characteristics,toxicity, and complications were outlined. In multivariate regression analyses of pre-treatment variables from a prospective database, predictors for tumor response and survival after TACE were determined. REsULTs: 112 TACE courses were performed (2.4±1.5 courses per patient). Mean maximum tumor size was 75 (± 43) mm, in 68% there was bilobar disease. Best response to TACE treatment was: progressive disease (PD) 9%, stable disease (sD) 55%, partial remission (PR) 36%, and complete remission (CR) 0%. Multivariate regression analyses identified tumor size ≤75 mm, tumor number ≤5, and tumor hypervascularization as predictors for PR. The overall 1-, 2-, and 3-year-survival rates were 75%, 59%, and 41%, respectively, and the median survival was 26 months. Low α-fetoprotein levels (s ratio=3.3) and PR as best response to TACE (Odds ratio=6.7) were significantly associated with long term survival (>30 months, R2=36%). Grade 3 toxicity occurred in 7.1% (n=8), and grade 4 toxicity in 3.6% (n=4) of all courses in terms of reversible leukopenia and thrombocytopenia. The incidence of major

关键词： carcinoma, hepatocellular transarterial chemoembolization degradable starch microspheres Lipiodol tumor response survival

Improvement of center segregation in high-carbon steel billets using soft reduction

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Journal of University of science and Technology Beijing 2006年第6期13卷 490-496页

作者： Wenjun Wang Xionggang Hu Linxin Ning Raimund Bülte Wolfgang bleck Institute of Ferrous Metallurgy RWTH Aachen University Intzestrasse 1 52072 Aachen Germany shougang Group Research Institute Beijing 100041 China

Center segregation is the main reason for cup fracture of high-carbon wire rod during drawing. Therefore, to continuously produce cast billets with very low center segregation is an important objective. The soft reduction technology is considered to be an effective method to minimize center segregation. To elucidate the effect of soft reduction on the internal quality of high-carbon steel billets, soft reduction was applied with different solid fractions in the core area of billets in a laboratory casting machine. A coupled temperature/displacement finite element model was developed to calculate the solid fraction using the commercial software ABAQUs. Center segregation, center porosity, homogeneity of elements, and equiaxed crystal zone were obviously improved by applying soft reduction, especially when the solid fraction was less than 1.0. The optimal results were obtained when the solid fraction was approximately 0.9.

关键词： steel 100Cr6 centre segregation soft reduction finite element model internal cracks

Transcutaneous perianal sonography:A sensitive method for the detection of perianal inflammatory lesions in Crohn's disease

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World Journal of Gastroenterology 2004年第19期10卷 2859-2863页

作者： Jochen Wedemeyer Timm Kirchhoff Gernot sellge Oliver Bachmann Joachim Lotz Michael Galanski Michael P.Manns Michael J.Gebel Jrg s.bleck Department of Gastroenterology Hepatology and EndocrinologyMedical School of HannoverCarl Neuberg Str.130623 HannoverGermany M.D. Department of Diagnostic Radiology Medical School of HannoverCarl Neuberg Str.130623 HannoverGermany Department of Gastroenterology Hepatology and EndocrinologyMedical School of HannoverCarl Neuberg Str.130623 HannoverGermany

AIM:Pelvic magnetic resonance imaging(MRI)and endoanal ultrasound which are established imaging methods for perianal inflammatory lesions in patients with Crohn's disease require expensive specialized equipments and *** investigated the feasibility and sensitivity of transcutaneous perianal ultrasound(PAUs)using regular ultrasound probes in the imaging of perianal inflammatory *** sonographic findings were correlated to pelvic MR]-scans. METHODs:We performed PAUs in 25 patients with Crohn's disease and clinical signs of perianal inflammatory disease. Wibhin a median of 10 d(range 0-75)these patients underwent MRI of the *** convex and linear high resolution probes were used for *** sonographic findings were correlated to the MRI findings by blinded investigators. REsULTs:The sonographic investigations were well tolerated by all *** typically presented as hypoechoic ***-nine fistulae were detected in 22 *** were detected in 7 patients and presented as hypo-or anechoic ***-six of 29 fistulae and 6 of 7 abscesses could be confirmed by *** statistics showed an excellent agreement (kappa>0.83)between the two imaging methods. CONCLUsION:PAUs is a simple,painless,feasible,real- time method that can be performed without specific patient preparation which is comparable in its sensitivity to pelvic MRI in the detection of perianal fistulae and/or abscesses. PAUs can especially be recommended as a screening tool in acute perianal disorders such as perianal abscess and for follow-up studies of perianal inflammatory disease.

关键词： Anal Canal histology Anus Diseases Crohn Disease Humans Inflammation Ultrasonography, Doppler, Color

Multiphase-field simulation of austenite reversion in medium-Mn steels

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 847-853页

作者： Yan Ma Rui Zheng Ziyuan Gao Ulrich Krupp Hai-wen Luo Wenwen song olfgang bleck steel Institute(IEHK) RWTH Aachen UniversityIntzestraße 152072 AachenGermany Department of Ferrous Metallurgy University of Science and Technology BeijingBeijing 100083China Max-Planck-Institut für Eisenforschung GmbH(MPIE) Max-Planck-Straße 140237 DüsseldorfGermany

Medium-Mn steels have attracted immense attention for automotive applications owing to their outstanding combination of high strength and superior *** steel class is generally characterized by an ultrafine-grained duplex microstructure consisting of ferrite and a large amount of *** a unique microstructure is processed by intercritical annealing,where austenite reversion occurs in a fine martensitic *** the present study,austenite reversion in a medium-Mn alloy was simulated by the multiphase-field approach using the commercial software MICREss®coupled with the thermodynamic database TCFE8 and the kinetic database *** particular,a faceted anisotropy model was incorporated to replicate the lamellar morphology of reversed *** simulated microstructural morphology and phase transformation kinetics(indicated by the amount of phase)concurred well with experimental observations by scanning electron microscopy and in situ synchrotron high-energy X-ray diffraction,respectively.

关键词： medium-Mn steels intercritical annealing austenite reversion phase-field simulation faceted anisotropy model

Correlates of long-term physical activity adherence in women

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Journal of sport and Health science 2017年第4期6卷 434-442页

作者： Haichun sun Cheryl A. Vamos sara s.B. Flory Rita DeBate Erika L. Thompson Jennifer bleck Department of Teaching and Learning College of Education University of South Florida Tampa FL 33620 USA Department of Community and Family Health College of Public Health University of South Florida Tampa FL 33612 USA

Background: Little is known about the factors that may influence women's adherence to moderate-to-vigorous physical activity(MVPA) using longitudinal data. The purpose of this study was to examine the correlates of long-term physical activity(PA) participation among ***: Female data from Waves I, III, and IV(n = 5381) of the National Longitudinal study of Adolescent to Adult Health(Add Health) were used for the analysis. The outcome of PA adherence was operationalized as(1) consistently physically active(at least 5 instances during the week)in both Waves III and IV(during adulthood), and(2) consistently not physically active or only physically active in either Wave III or IV. Predictor variables from Wave I(during adolescence) included race/ethnicity, PA level, self-perception of being physically fit, general health status, attempt to change weight, parents' income level, parents' education, well-being, depression, access to PA resources, days of physical education(PE), and grade level. Crude and adjusted logistic regression models were utilized to estimate the adjusted odds ratio(a OR) and 95% confidence interval(95%CI) for the outcome ***: PA levels during adolescence significantly predicted PA adherence(a OR = 1.67, 95%CI: 1.35–2.05). Additionally, wanting to lose weight(a OR = 1.49, 95%CI: 1.20–1.85), using fitness center in the neighborhood(a OR = 1.29, 95%CI: 1.05–1.58), and having 5 days of PE a week(a OR = 1.48, 95%CI: 1.09–2.02) were significant predictors. Women who did not perceive being physically fit(a OR = 0.65, 95%CI: 0.44–0.95)and Black, non-Hispanics(a OR = 0.60, 95%CI: 0.44–0.82) were less likely to adhere to ***: The findings suggested that physically active adolescents were more likely to become active adults. Future research should address interventions(e.g., PE program, community resources) that may promote lifetime PA in women, with the goal of decreasing morbidity and mortality.

关键词： Females Longitudinal Moderate-to-vigorous physical activity social ecological frameworks