The Influence of Vanadium Additions on Isothermally Formed Bainite Microstructures in Medium Carbon Steels Containing Retained Austenite
The influence of V additions on isothermally formed bainite in medium carbon steels containing retained austenite has been investigated using in-situ high energy X-ray diffraction (HEXRD) and ex-situ electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis (EDX) techniques in the transmission electron microscope (TEM). No significant impact of V in solid solution on the bainite transformation rate, final phase fractions or on the width of bainite laths was seen for transformations in the range 375–430 °C. No strong influence on the dislocation density could be detected, although quantitative analysis was impeded by ferrite tetragonality. A reduction in the carbon content of retained austenite Cγ that is not believed to be due to competition with VC or cementite precipitation was observed. No influence of V on the carbon supersaturation in bainitic ferrite Cb could be directly measured, although carbon mass balance calculations suggest Cb slightly increases. A beneficial refinement of blocky MA and a corresponding size effect induced enhancement in austenite stability were found at the lowest transformation temperature. Overall, V additions result in a slight increase in strength levels.
bainite; vanadium microalloying; austenite stability; HEXRD; EELS
Irina Pushkareva (1), Babak Shalchi-Amirkhiz (1), Sébastien Yves Pierre Allain (2), Guillaume Geandier (2), Fateh Fazeli (1), Matthew Sztanko (1) and Colin Scott (1)
(1) Canmet Materials, Natural Resources Canada, 183 Longwood Road South, Hamilton, ON L8P 0A5, Canada
(2) Institut Jean Lamour, UMR CNRS-UL 7198, 54011 Nancy, France
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Metals, Vol. 10, no. 3, 2009, 392.