Effects of niobium on mechanical twinning and tensile properties of a high Mn twinning-induced plasticity steel

The effects of Nb on mechanical twinning and tensile deformation behavior were investigated in hot-rolled Fe18Mn0.6C1.5Al twinning-induced plasticity (TWIP) steels without and with 0.1Nb. In comparison to the Nb-free TWIP steel with fully-recrystallized and equiaxed grains, the Nb-added TWIP steel showed non-recrystallized and elongated grains with well-dispersed NbC particles and a high density of dislocations. The increased yield and tensile strengths in the Nb-added TWIP steel were mainly caused by the hardening of dislocations in non-recrystallized grains rather than the precipitation hardening of NbC particles or the solid solution hardening of Nb atoms. Meanwhile, the uniform elongation and strain hardening rate of the Nb-added TWIP steel were decreased due to inactive mechanical twinning, which is probably because the dislocations interfere with the movement and dissociation of dislocations necessary for mechanical twinning.