The effect of silicon on the nanoprecipitation of cementite

Abstract

The current work presents a comprehensive study that aims at understanding the role of silicon on θ precipitation, as well as on the ε → θ carbide transition in tempered martensite. Cementite nucleation was modelled under paraequilibrium conditions in order to ensure silicon's presence in the carbide, where both thermodynamic and misfit strain energies were calculated to evaluate the overall free energy change. The growth stage was investigated using in situ synchrotron radiation; three alloys containing a wide range of silicon contents have been studied. Silicon appears to play a significant role on carbide growth. It was observed throughout tempering that as silicon content increased in the alloy, cementite precipitation was slower. Literature reports that cementite growth is accompanied by silicon partitioning, where the silicon content inside the carbide decreases as tempering progresses. Therefore it appears that the limiting factor of the growth kinetics is the rate at which silicon is being rejected from the carbide, which piles up at the carbide/matrix interface, acting as a barrier for further growth.

Predicting the cooperative effect of Mn–Si and Mn–Mo on the incomplete bainite formation in quaternary Fe–C alloys

“…For Fe-0.43C-3.0Mn-2.12Si alloy, Figure 5(a), the experimental values of C g stasis are close to the GEB model predictions but below the T ′ 0 model assuming a strain energy of 400 J/mol. The high Si content in this system is known to suppress carbide formation [26,27], hence neglecting the carbide formation in the GEB model is an accurate assumption for this system. In Fe-0.1C-1.5Mn-0.3Mo alloy, Figure 5(b), the experimental values of C g stasis are much lower than the predictions by the GEB model but correspond better to the predictions of the T 0 and T ′ 0 model (assuming a strain energy of 200 J/mol) predictions.…”

Prediction and Validation of the Austenite Phase Fraction upon Intercritical Annealing of Medium Mn Steels

“…Although Si is known to retard the cementite formation, however, it does not completely suppress the precipitation and cementite will appear after a long annealing times. [56,57] It is worth noting that considering the observed effect of simulation cell size on the predicted value of f c , it is clear that varying the cell size does not affect the overall trend of predicted fractions for both c fi a and the a¢ fi c transformations. In the current analysis, the cell length of a¢ fi c is taken the same as the c fi a transformation, i.e., 50 lm.…”

Study of the decomposition behavior of retained austenite and the partitioning of alloying elements during tempering in CMnSiAl TRIP steels

“…It was well reported that e-carbide was usually precipitated at the early stage of martensite tempering followed by carbide transition from e-carbide into cementite [23,24].…”