Effects of cerium addition on the microstructure, mechanical properties and strain hardening behavior of TWIP steel Fe-18Mn-0.6C

The effects of cerium (Ce) on the microstructure, mechanical properties and strain hardening behavior of Fe18Mn-0.6C twin-induced plasticity (TWIP) steel were investigated by electron backscatter diffraction, X-ray diffraction and transmission electron microscopy. Compared with the addition of Al, the addition of Ce significantly reduced the stacking fault energy of TWIP steel, which promotes the formation of deformation and annealing twins. The dynamic strain aging behavior of TWIP steel was inhibited by Al and Ce atoms during plastic deformation. The optimal mechanical properties were obtained when 0.015 wt% of Ce was added, resulting in a tensile strength of 1023 MPa; and an elongation was 92%. The interaction of twin variants in the Ce-containing alloys exhibited an X shape, which was significantly different from the T shape in the non-Ce containing alloy. This is mainly attributed to the fact that Ce promotes dislocations near grain boundaries, where for the nucleation of deformation twins at grain boundaries is favored. Compared with the T-shaped twin variants, the dynamic Hall-Petch effect caused by the X-shaped staggered twin variants was stronger, which improved the strain hardening ability of TWIP steel.