Effect of Al and B Alloying on Phase Transformation in Nb Microalloyed Q&P Steels




Abstract: The effect of Al and B on phase transformations in a 0.3C-2.0Mn-1.2Si steel during Quench and Partitioning (Q&P) annealing cycle was evaluated. Decomposition of austenite was studied by dilatometry. The interpretation of phase transformations during cooling was supported by SEM metallography. It is shown that alloying additions strongly affect ferrite formation during continuous cooling and austenite transformation to bainite during isothermal holding. Formation of martensite during cooling before isothermal holding accelerates and enhances decomposition of austenite to bainite. The temperature of isothermal holding that ranged from 450 to 350 oC significantly affects bainite formation and bainite morphology. Additional alloying of Nb containing steel with Al and TiB retards bainite formation leading to a lower fraction of retained austenite in the final structure.

Authors: O. Girina, O. Yakubovsky, D. Panahi, and S. Jansto

Keywords: bainite transformation, tempering, dilatometry, retained austenite

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9 pages


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