Investigation into the structural evolutions of a low alloy steel during tempering

Abstract

Abstract The structural transformations occurring during tempering in a high strength, low alloy steel containing 1.72 wt.%Si were studied using various and complementary methods of analysis such as differential dilatometry, hardness measurements, X-ray diffraction experiments and transmission electron microscopy (TEM), In situ TEM observations were performed in order to determine the transformation mechanisms involved. Two different structural states of the steel were considered (water and air quenched from the γ field). Furthermore, changes in mechanical properties were also characterized in various tempered states. A single tempering carried out at 300 °C for 2 h seems to be sufficient to produce the complete decomposition of the retained austenite (air-quenched state) and to lead to the best compromise of mechanical properties.