Influence of Co and Al on Bainitic Transformation in Super Bainitic Steels

Abstract

The effect of cobalt and aluminum addition on the bainitic transformation of super bainitic steels was investigated. Nanostructured bainitic ferrite and retained austenite microstructures were obtained when the steels were transformed at low temperatures. The bainitic transformation was accelerated by the addition of Co and Al. The thickness of bainite plate was reduced and the volume fraction of bainite was increased in the Co and Al containing steel, compared with the parent steel.

The Effects of Cr and Al Addition on Transformation and Properties in Low‐Carbon Bainitic Steels

“…Therefore, more undercooled austenite can transform into lath-like BF in the Cr addition steel, which leads to the improvement of the mechanical properties of steel B. Figure 7 shows that bainite transformation is accelerated by Al addition, which is consistent with the results by Hu et al [14,15], Caballero et al [37] and others. SEM micrographs (Figure 4) indicate that steel B (Cr steel) mainly consists of bainite sheaves without ferrite, while a small amount of ferrite presents in steel C (Cr +Al steel), showing that Al addition promotes the formation of ferrite.…”

“…For example, Jimenez-Melero et al [5] and Zhao et al [12] reported that the addition of Al significantly increases the chemical driving force for the formation of bainitic ferrite plates and shortens the austenite-to-bainite transformation time. Similar results were also obtained by Garcia-Mateo et al [13] and Hu et al [14,15]. They claimed that the addition of Co and Al accelerates the bainitic transformation by increasing the free energy…”

“…completes quickly in the three low-carbon steels in the present study. This is contrast to high-carbon steels in which several hours or days are needed to finish bainitic transformation [13,15]. …”

“…Some researchers have investigated the effect of Al addition on bainitic transformation [5,[12][13][14][15][16][17]. For example, Jimenez-Melero et al [5] and Zhao et al [12] reported that the addition of Al significantly increases the chemical driving force for the formation of bainitic ferrite plates and shortens the austenite-to-bainite transformation time.…”

Method to Evaluate the Kinetics of Bainite Transformation in Low-Temperature Nanobainitic Steel Using Thermal Dilatation Curve Analysis

“…However, the prolonged transformation time hinders its application [12]. A great deal of research has been conducted to understand the effect of ausforming conditions [13][14][15][16], chemical compositions [17], and isothermal temperature [18] on the kinetics and mechanical properties. Obtaining bainitic microstructure is fundamental, and involves the chance to exhibit a good mechanical performance.…”