ժҪ Stress relaxation method was carried out on a Ti micro- alloyed interstitial- free (IF) steel at the temperature ranging from 800 to 1000 ��. The results show that the softening kinetics curves of deformed austenite can be divided into three stages. At the first stage, the stress has a sharp drop due to the onset of recrystallization. At the second stage, a plateau appears on the relaxation curves indicating the start and finish of strain- induced precipitation. At the third stage, the stress curves begin to descend again because of coarsening of precipitates. Precipitation- time- temperature (PTT) diagram exhibited a ��C�� shape, and the nose point of the PTT diagram is located at 900 �� and the start precipitation time of 10 s. The theoretical calculation shows that the strain- induced precipitates were confirmed as almost pure TiC particles. The TiC precipitates were heterogeneously distributed in either a chain- like or cell- like manner observed by transmission electron microscopy (TEM), which indicates the precipitates nucleated on dislocations or dislocation substructures. In addition, a thermodynamic analytical model was presented to describe the precipitation in Ti micro- alloyed IF steel, which shows a good agreement between the experimental observation and the predictions of the model.
Abstract��Stress relaxation method was carried out on a Ti micro- alloyed interstitial- free (IF) steel at the temperature ranging from 800 to 1000 ��. The results show that the softening kinetics curves of deformed austenite can be divided into three stages. At the first stage, the stress has a sharp drop due to the onset of recrystallization. At the second stage, a plateau appears on the relaxation curves indicating the start and finish of strain- induced precipitation. At the third stage, the stress curves begin to descend again because of coarsening of precipitates. Precipitation- time- temperature (PTT) diagram exhibited a ��C�� shape, and the nose point of the PTT diagram is located at 900 �� and the start precipitation time of 10 s. The theoretical calculation shows that the strain- induced precipitates were confirmed as almost pure TiC particles. The TiC precipitates were heterogeneously distributed in either a chain- like or cell- like manner observed by transmission electron microscopy (TEM), which indicates the precipitates nucleated on dislocations or dislocation substructures. In addition, a thermodynamic analytical model was presented to describe the precipitation in Ti micro- alloyed IF steel, which shows a good agreement between the experimental observation and the predictions of the model.
2016, Vol. 23 
