Austempering is an important thermal processing operation, where strong and tough bainitic steel is produced in a single heat treatment [1, 2]. During the austempering process, the steel is first austenitized and then cooled rapidly just above the martensite start temperature until bainite nucleates and grows, usually until the transformation stops and then it is cooled to room temperature. Due to the sluggish solid-state transformation kinetics, industrial austempering necessitates isothermal holds of 2–24 h, depending on the size and composition of steel. In contrast to conventional isothermal processing, cyclic thermal processing has been shown to accelerate the kinetics of several phase transformations [3–5], with a significant beneficial impact on productivity and energy consumption of these energy intensive operations. This was attributed to the non-isothermal effects resulting from cyclic treatment. The non-isothermal effect on phase transformations has also been utilized to enhance the productivity of a modern batch annealing operation [6]. In the present work, the effect of cyclic processing on austempering kinetics has been compared with conventional isothermal processing for 1080 steel. Furthermore, the effect of cyclic frequency on the austempering kinetics has been studied. Austempering kinetics experiments were performed on 6 mm diameter cylindrical samples of a 1080 steel using a Gleeble 3500 thermo-mechanical simulator (DSI Poestenkill, NY). A diametrical dilatometer was mounted on the specimen to measure the diameter change during the thermal processing. The austempering experiments were performed in two cycles, where the first cycle provides the same initial microstructure prior to each experiment. After completing the first cycle, the cylindrical specimens were heated to the austenitizing temperature (850 C), held for 5 min and then cooled to different austempering temperatures, where the bainite transformation was monitored for the desired period of time, followed by cooling to room temperature. The cooling rate was sufficiently fast to avoid any transformation occurring before reaching the austempering temperature (Fig. 1). The isothermal experiments were carried out at austempering temperatures of 260 and 300 C, whereas the cyclic experiments were carried out between 260 C and 300 C at two different heating/ cooling rates of 1 and 5 C/min. The percentage of bainitic transformation as a function of time was computed from the dilation curve [2] in conjunction with the microstructural examination by optical microscopy and SEM. The normalized dilatation curves for isothermal austempering at 260, 300 C, and cyclic austempering between 260 C and 300 C for 1 C/min and 5 C/min are shown in Fig. 2. In this figure, only the portion of the curve corresponding to austempering is shown and the dilatation curve has been offset to start at zero. The plateau of the dilatation curve with respect to the time represents the end of the transformation to bainite. It must be noted that the end of the bainite transformation does not necessarily correspond to 100% volume fraction of bainite [1]. Previously, using the same type of Gleeble experiments, it was shown that the end of the transformation corresponds closely to the austenite carbon content corresponding to a T0 equal to the austempering temperature [2, 7]. Furthermore the transformation dilatation at the end of the V. Sista P. Nash (&) Thermal Processing Technology Center, IIT, 10 W 32nd St., Chicago, IL 60616, USA e-mail: philip.nash@iit.edu