Effect of isochronal annealing on the microstructure, texture and mechanical properties of a cold-rolled high manganese steel

A Fe-17Mn-3Al-2Si-1Ni-0.06C wt.% steel was subjected to cold-rolling to 42% thickness reduction and isochronally annealed for 300 s between 500 and 850 °C. The high Mn steel was characterised via electron back-scattering diffraction, transmission electron microscopy and uniaxial tensile testing. The reversion of deformation-induced ε and α′-martensite to austenite (γ) was witnessed with the formation of fine twins in reverted/recovered γ grains after annealing to 650 °C. The nucleation of new γ grains at the boundary of reverted/recovered γ grains was also noted. Upon reversion, the γ orientations originated from the ε and α′-martensite orientations by phase transformation via the Shoji-Nishiyama and Kurdjumov-Sachs orientation relationships, respectively. Upon segmenting the γ grains, the recrystallised γ grains were observed to nucleate with orientations similar to those of the reverted/recovered γ grains. Uniaxial tension on a fully recrystallised γ microstructure showed that the initial γ grain size has a more significant effect on the yield strength than the ε and α′-martensite fractions. On the other hand, the initial ε and α′-martensite fractions affect the total elongation.