Homogeneously introducing more and thinner nanotwins by engineering annealing twin boundaries: A TWIP steel as an example

It is a challenge to homogeneously introduce more and thinner nanotwins into bulk materials. Our results showed that more and thinner deformation nanotwins could be more homogeneously introduced in a bulk solution-treated FeMnSiC twinning-induced plasticity (TWIP) steel after significantly reducing boundaries of annealing twins by thermomechanical processing that consisted of three cycles of deformation at room temperature (RT) and subsequent annealing. After introducing the recovery-annealed deformation nanotwins by 30% deformation at RT and annealing at 673 K, the three-time-trained steel showed a similar ductility comparable to the solution-treated steel but obtained 125 MPa higher in yield strength. The engineering annealing twins will open a promising pathway for strengthening bulk TWIP steels by homogeneously introducing thinner recovery-annealed deformation nanotwins.