| Abstract Scope |
The final microstructure and consequently the properties of hot-rolled steels are largely determined by the decomposition of austenite during controlled cooling. For the development of advanced steels, it is therefore important to quantitatively predict the behaviour of austenite decomposition in a wide range of conditions, which requires accurate and robust experimental methods for the measurement of decomposition kinetics. In the present work, two techniques, i.e. traditional dilatometry and laser ultrasonics, were employed to quantify the decomposition kinetics of selected low-carbon niobium microalloyed steels. A systematic investigation was performed on the effect of niobium, austenite grain size, work-hardening, and cooling rate on the decomposition kinetics. Laser ultrasonic measurements were found to be consistent with dilatometry, with the additional benefit of monitoring austenite grain conditioning during the thermomechanical treatment prior to decomposition. Thus, laser ultrasonics provides a valuable tool to in-situ monitor the sequence of microstructural changes during hot rolling of steel. |