Analysis on bainite transformation in reheated low-carbon bainite weld metals

Abstract

A combination of laser scanning confocal microscopy (LSCM) and dilatometry was utilised to simultaneously qualitatively analyse the morphological evolution of bainite by examination of in situ observed micrographs and to quantitatively investigate the amount of bainite transformation by studying dilatometry data. Shorter bainite structures form for smaller prior austenite grain sizes and lower cooling rates, which causes greater bainite transformation to occur in the latter stages of the transformation process. On the other hand, the amount of lath-shape sub-structure increases due to a higher cooling rate. In addition, the surface relief presents greater height and the peak and valley values stay farther away from the horizontal line for specimens at a higher cooling rate. In addition, a lower strain energy per unit volume gives rise to greater bainite transformation compared to that from abundant driving forces.