(56b) Accumulative Roll Bonding (ARB)-Processed High-Manganese Twinning Induced Plasticity (TWIP) Steel with Extraordinary Strength and Reasonable Ductility

Accumulative roll bonding (ARB) process at room temperature was used to fabricate a nanostructured twinning-induced plasticity (TWIP) steel. The effect of the number of ARB cycles from 1 to 3 on the microstructure and mechanical properties of Fe-31Mn-3Al-3Si (wt%) TWIP steel was investigated. The results showed that the microstructure of the 1-cycle ARB-processed sample mainly contained the primary and secondary mechanical twins. However, in the microstructure of 2-cycle ARB-processed sample, new configurations of small nanotwins which they are known as the hierarchical nanotwinned (HNT) structures were observed between the secondary mechanical twins. In the microstructure of 3-cycle ARB-processed sample, new subdivided grains with a mean size of about 100 nm were produced. Additionally, the 3-cycle ARB-processed TWIP steel sample exhibited extraordinary strength (about 1.2 GPa) and reasonable ductility (about 15%). The mechanical behavior of ARB-processed TWIP steel was interpreted as the evidence for microstructural features such as the mechanical twins (especially, the HNT structures) and nano/ultrafine grains.