Deformation behavior of duplex austenite and <i>ε</i>-martensite high-Mn steel

Abstract

Deformation and work hardening behavior of Fe-17Mn-0.02C steel containing <i>ε</i>-martensite within the austenite matrix have been investigated by means of <i>in situ</i> microstructural observations and x-ray diffraction analysis. During deformation, the steel shows the deformation-induced transformation of austenite → <i>ε</i>-martensite → <i>α</i>'-martensite as well as the direct transformation of austenite → <i>α</i>'-martensite. Based on the calculation of changes in the fraction of each constituent phase, we found that the phase transformation of austenite → <i>ε</i>-martensite is more effective in work hardening than that of <i>ε</i>-martensite → <i>α</i>'-martensite. Moreover, reverse transformation of <i>ε</i>-martensite → austenite has also been observed during deformation. It originates from the formation of stacking faults within the deformed <i>ε</i>-martensite, resulting in the formation of 6H-long periodic ordered structure.