An analysis of the deformation characteristics of a dual phase twinning-induced plasticity steel in warm working temperature regime

The deformation behavior of a dual phase twinning induced plasticity (TWIP) steel has been studied by means of continuous heating compression (CHC) testing technique. This has been performed in the range of room temperature to 300 °C (warm working regime) and the related experimental flow behavior has been compared with the theoretical ones. The derived deviations at 45 ± 5 °C, 100 ± 5 °C and 165 ± 5 °C have been properly addressed considering the related microstructural evolutions. The optical and scanning electron microscopy along with feritscope measurements have been carried out to explore the basis of any deviation. The results demonstrate the formation of ferrite at the austenite grain boundaries through deformation induced ferrite transformation mechanism. This effectively makes the structure softer at the initial stage of deformation (deviation i, 45 ± 5 °C). The initiation of twins within the austenite grains results in strengthening the structure and a small bump appears in the θ–ε curve (deviation ii, 100 ± 5 °C). In addition the responsible deformation mechanism of the steel is believed to change from mechanical twinning to dislocation slip at about 160 °C thereby a local decrease in the rate of work hardening occurs (deviation iii, 165 ± 5 °C).

► Appearance of deviations from the theoretical behavior during continuous heating compression.
► Occurrence of deformation induced ferrite transformation at the austenite grain boundaries.
► Initiation of mechanical twins in austenite grains after second deviation (100 ± 5 °C).
► Changing the dominant deformation mechanism by increasing temperature to about 165 °C.
► Increasing of the ferrite volume fraction by increasing the level of strain.