Effects of rare earth addition on microstructure and mechanical properties of a Fe-15Mn-1.5Al-0.6C TWIP steel

The microstructure and mechanical properties of a Fe-15Mn-1.5Al-0.6C TWIP steel with and without rare earth (RE) addition were investigated. The RE-alloyed steel showed both improved tensile strength and total elongation (TEL). Optical microscopy and electron back-scattered diffraction (EBSD) characterizations showed that the RE-alloyed steel possessed a more homogeneous microstructure and a larger fraction of high-angle grain boundaries, which increased the TEL. Meanwhile, EBSD and transmission electron microscope (TEM) analyses indicated that the RE-alloyed steel exhibited more uniform distributed annealing twins and secondary annealing twins with a thickness of 10-20 nm appeared in some grains, which resulted in the higher tensile strength.