Effect of isothermal holding temperature on retained austenite fraction in medium-carbon Nb/Ti-microalloyed TRIP stee

• Autorzy: Grajcar A. , Krztoń H.
• Języki publikacji: EN

Abstrakty

EN

Purpose: The aim of the paper is to determine the effect of the isothermal holding temperature in a bainitic transformation range on a fraction of retained austenite for a new-developed medium-carbon TRIP steel containing Nb and Ti microadditions. Design/methodology/approach: The thermo-mechanical processing was carried out by a multi-stage compression test using the Gleeble thermomechanical simulator. The steel was subjected to 5 variants of processing with an isothermal bainitic transformation temperature in a range from 250 to 450°C. Identification of structural constituents was done using microscopic observations and X-ray diffraction. To determine the fraction of retained austenite the Rietveld method was applied. Findings: It is possible to obtain a high fraction of retained austenite characterized by the high thermodynamic stability in a C-Mn-Si-Al steel containing 0.43% C. The maximal fraction of austenitic phase equal above 20% was obtained for the wide temperature range of isothermal holding from 350 to 450°C. The maximal carbon content in the retained austenite equal 1.84 wt.% is present for the temperature range from 350 to 400°C. Below 350°C due to relatively low carbon diffusivity and high Msγ temperature, a part of austenite transforms to marteniste. Above 400°C there is still a high fraction of retained austenite but it contains a lower C content. Practical implications: The obtained austenite volume fraction and carbon content in a γ phase determined as a function of isothermal holding temperature can be useful in optimization of thermo-mechanical processing conditions for medium-C TRIP steels. Originality/value: The research was performed on a new-developed medium-carbon Si-Al steel microalloyed with Nb and Ti. There is a lack of data on microstructure and stability of retained austenite in such advanced group of high-strength TRIP steels.

Słowa kluczowe

EN

metallic alloys; TRIP steel; thermomechanical processing; hot-temperature deformation; retained austenite; microalloying; bainitic steel; Rietveld method

• Wydawca: International OCSCO World Press
• Czasopismo: Journal of Achievements in Materials and Manufacturing Engineering
• Rocznik: 2011
• Tom: Vol. 49, nr 2
• Strony: 391--399
• Opis fizyczny: Bibliogr. 44 poz., rys., tab.

Twórcy

autor

Grajcar A.

• Division of Constructional and Special Materials, Institute of Engineering Materials and Biomaterials, Institute of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland b Institute for Ferrous Metallurgy, ul. K. Miarki 12, 44-100 Gliwice, Poland

autor

Krztoń H.

• Institute for Ferrous Metallurgy, ul. K. Miarki 12, 44-100 Gliwice, Poland

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