In order to reduce CO2 emissions, the steel industry shifts its production towardthe usage of higher scrap contents. This transformation leads to an elevation oftramp element concentrations, which can alter the steel’s response during heattreatments. In this work, the phase transformation behavior of a hypoeutectoid steelgrade is studied. A reference alloy from the blast furnace route is compared to alloyswith increased tramp element concentrations. Dilatometry experiments are performedto obtain information about phase transformations. Additionally, themicrostructure is examined with hardness measurements, optical as well asscanning electron microscopy including electron backscatter diffraction. Moreover,in situ high-energy X-ray diffraction measurements deliver information of themicrostructural evolution during the heat treatment and provide a precise overviewof the evolved phases after cooling. Finally, the prior austenite grain size is determinedwith a high-temperature laser scanning confocalmicroscope and is correlatedto the observed phase transformation alterations. The examination of microstructuresreveals that an increase in tramp element contents facilitates the formation ofdisplacive phases along with retained austenite. Furthermore, it is observed thattramp elements impede the growth of prior austenite grains by segregating to thegrain boundaries at high temperatures, thereby inducing a solute drag effect.
Hatzenbichler et al. (Wed,) studied this question.