Effect of ECAP processing temperature on an austenitic TWIP steel's microstructure, texture and mechanical properties

The development of microstructure and texture of twinning-induced plasticity (TWIP) steel sheet during ECAP at two temperatures (250 degrees and 350 degrees) up to four passes were investigated. The high chromium content is the differential of this TWIP steel, a chemical element that reduces the stacking-fault energy and increases corrosion resistance. By imposing ECAP, the volume fraction of twins, dislocation density, and yield strength significantly increase while ductility decreases. This study compared the effect of temperature during applied severe plastic deformation (SPD). Thin parallel slip bands' high density was observed, and in addition to an intense micro shear, banding took place when pressing was continued by increasing the number of passes. The martensitic transformation was not detected in the deformation-twinning microstructure after more passes. The relationship between the microstructure, strain-hardening behavior, and mechanical properties was investigated after two different deformation schedules of ECAP. The best balance between high strength and good ductility (1915 MPa and 7%) was obtained after four passes at 250 degrees C and 350 degrees C. It was found that the quantity of ECAP pass affects the displacement substructure with the formation of shear bands, subgrains, and various variants of twins. These also influenced strain-hardening behavior, microhardness, texture, and ultimate strength.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The development of microstructure and texture of TWIP steel sheet during ECAP at different temperatures were studied, and the effect of temperature during the severe plastic deformation process was compared. The results showed that the volume fraction of twins, dislocation density, and yield strength increased while ductility decreased after ECAP. The best balance between high strength and good ductility was achieved after four passes at 250 degrees C and 350 degrees C.