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Influence of Al, Cu and Ni Additions on Mechanical Properties of Hot-Rolled Fe-9Mn-0.2C Medium-Manganese Steels

Yoon Young-Chul, Kim Sang-Gyu, Lee Sang-Hyeok, Hwang Byoungchul

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

1007--1011

EN

The microstructure and mechanical properties of hot-rolled Fe-9Mn-0.2C medium-manganese steels with different Al, Cu, and Ni contents were investigated in this study. Based on the SEM, XRD, and EBSD analysis results, the microstructure was composed of martensite, band-type delta ferrite, and retained austenite phases depending on the Al, Cu, and Ni additions. The tensile and Charpy impact test results showed that the sole addition of Al reduced significantly impact toughness by the presence of delta-ferrite and the decrease of austenite stability although it increased yield strength. However, the combined addition of Al and Cu or Ni provided the best combination of high yield strength and good impact toughness because of solid solution strengthening and increased austenite stability.

2

Obróbka cieplna stali średniomanganowych dla motoryzacji

Grajcar Adam, Morawiec Mateusz, Skowronek Adam

Stal, Metale & Nowe Technologie

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2019

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nr 7-8

12--18

PL

Nowoczesne materiały konstrukcyjne wykorzystywane w branży automotive powinny łączyć wysoką wytrzymałość z dobrą formowalnością – są to własności do niedawna wykluczające się. Z drugiej strony koszty produkcji muszą być relatywnie niskie, gdyż aspekt ekonomiczny jest niezwykle ważny w obecnych czasach. Wymienione własności wytrzymałościowe można uzyskać dzięki rozdrobnieniu ziarna, jak również wygenerowaniu w stali austenitu szczątkowego, którego przemiana powoduje znaczne umocnienie materiału podczas odkształcenia. Koszty produkcji maleją wraz z ograniczeniem zawartości drogich dodatków stopowych. Cechy te wykazują stale średniomanganowe.

EN

Advanced structural materials used in the automotive industry should combine high strength and good formability – a pair of properties which until recently were mutually exclusive. On the other hand, production costs must be relatively low because the economic aspect is extremely important nowadays. The mentioned strength properties can be obtained due to grain refinement as well as the generation of retained austenite in steel, which is transformed during deformation causing the significant strain hardening of the material. Production costs decrease with the reduction of the content of expensive alloying elements. These features are the domain of medium manganese steels.

3

Strategie obróbki cieplnej dla zimnowalcowanych i gorącowalcowanych taśm z karoseryjnych stali średniomanganowych

Morawiec Mateusz, Grajcar Adam, Skowronek Adam, Kozłowska Aleksandra

Hutnik, Wiadomości Hutnicze

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2019

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Vol. 86, nr 8

267--271

PL

Przedstawiono strategie obróbki cieplnej dla karoseryjnych taśm ze stali średniomanganowych. Celem części badawczej było zbadanie wpływu temperatury wyżarzania międzykrytycznego z zakresu 680-800°C przez 1h na stabilizację austenitu szczątkowego w stali średniomanganowej. Materiałem wykorzystanym w eksperymencie była stal zawierająca 0,16% C, 4,7% Mn, 1,6% Al, 0,2% Mo, 0,2% Si. Zakres pracy obejmował badania dylatometryczne, twardości oraz obrazowanie na mikroskopie świetlnym i skaningowym. Wyżarzanie międzykrytyczne przeprowadzone w temperaturze 700 oraz 680°C umożliwiło wytworzenie w strukturze stabilnego austenitu szczątkowego.

EN

Heat treatment strategies for autobody medium-manganese steel sheets were presented. The aim of the research work was to investigate an effect of intercritical annealing temperature in a range of 680-800°C for 1h on the stabilization of retained austenite in a medium manganese steel. The material used in the experiment was a steel containing 0.16% C, 4.7% Mn, 1.6% Al, 0.2% Mo, 0.2% Si. The scope of the research included dilatometer tests, hardness tests and imaging using light and scanning electron microscopes. Intercritical annealing carried out at 700 and 680°C allowed forming some stable retained austenite in the structure.

4

Some aspects of the determination of retained austenite using the Rietveld refinement

Morawiec M.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 80, nr 1

11--17

EN

Purpose: The aim of the paper is to show the advantage of the application of the Rietveld refinement for determination of retained austenite amount in multiphase microstructure steels. Design/methodology/approach: The steels used for the investigation were thermomechanically rolled and controlled cooled to room temperature. The investigation of the microstructure was carried out using light microscopy. X-ray diffraction investigations of analyzed steel were a major part of the research. The phase identification and quantitative analysis of retained austenite were done using the HighScore Plus software that includes the Rietveld refinement method. The Rietveld analysis takes into account the preferred orientation that occurs during thermo-mechanical processing of steel. Findings: It was found that after the thermo-mechanical processing the microstructure of steel is composed of fine-grained bainitic matrix which includes bainite-austenite constituents, martensite blocks and some fraction of retained austenite. The X-ray diffraction showed that this steel includes phases of Feα (bainite and martensite) and Feγ (retained austenite). The Rietveld analysis showed that the volume fraction of retained austenite is 14.1%. Research limitations/implications: To confirm that Rietveld refinement method is a good tool for the quantitative analysis of retained austenite volume fraction EBSD measurements should be done for comparison purposes. Practical implications: The obtained results can be used for determination of retained austenite fraction in AHSS steels. It is important because the retained austenite content and its mechanical stability decide about a formability level of these steel grades. Originality/value: Some methodological aspects are concerned affecting the final quantitative results of retained austenite volume fraction is AHSS.