In Situ Characterisation of Austenite/Ferrite Transformation Kinetics and Modelling of Interphase Precipitation Inter-Sheet Spacing in V Microalloyed HSLA Steels

Abstract:

A new generation of low-carbon microalloyed High Strength Low Alloy (HSLA) steels has been developed to utilize a combination of single-phase ferritic microstructures and optimized interphase precipitation to provide high level strength and exceptional formability. The interphase precipitation reaction is a transient process lending itself strongly to take advantage of in-situ characterization techniques. The austenite/ferrite interface kinetics during isothermal transformation at 1003 K is measured using HT-CSLM, the pre-exponential effective mobility constant was found to be mobility 0.822 (m J)/(mole s). The V interphase precipitation is characterised using TEM at isothermal transformation temperatures of 923 and 973 K as having inter-sheet spacing of 22±7 and 32±9 nm respectively. Interphase precipitation inter-sheet-spacing is simulated using a revised Quasi-Ledge model and qualitatively predicts the observed trends observed for inter-sheet spacing. The results of in-situ characterisation and modelling suggest that it is possible to optimize the strengthening potential of the precipitation processes by controlling the thermal processing of microalloyed HSLA.

• Periodical: Materials Science Forum (Volume 879)
• Pages: 356-362
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.356
• Online since: November 2016
• Authors: Samuel Clark*, Yong Jun Lan, Vit Janik, Arjan Rijkenberg, Seetharaman Sridhar
• Keywords: HSLA, In Situ-HT-CLSM, Interphase Precipitation, Quasi-Ledge Model

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