In Situ Observation of the Pentectic Reaction and Transformation in a Commercial HSLA Steel

摘要

In situ experiments have been performed to investigate the peritectic reaction and transformation in a commercial HSLA steel. The characteristic temperature and interface migration behavior were recorded during the peritectic reaction and transformation were recorded during the cooling. The in situ observed results indicated that the austenite phase (γ) was observed to nucleate at the interface of the liquid and primary δ-ferrite phases. The intermediate y phase propagated along with the liquid/δ-ferrite interface and gradually isolated the liquid and primary δ-ferrite phases. Subsequently, the annular γ phase laterally grew toward the liquid and δ phases. Moreover, the occurrence of the peritectic reaction turned into a lower temperature as the cooling rate increased. In the peritectic transformation, the γ phase thickened toward both the liquid side and primary δ-ferrite side. The interface migration velocities during the peritectic transformation were obtained by measuring the migration distances of two interfaces versus time. The migration velocity of austenite/δ-ferrite (γ/δ) interface was significantly higher than that of liquid/austenite (L/γ) interface. Furthermore, an increase in the cooling rate accelerated the migration velocities of γ/δ and L/γ interfaces during the peritectic transformation.