This study was carried out to clarify the microstructure and mechanical properties of martensite transformed from ultrafine grained (UFG) austenite fabricated by the accumulative roll-bonding (ARB) process in an Fe-29.6wt.%Ni alloy. The sheet ARB processed by 5 cycles (equivalent strain:ε=4.0) showed the ultrafine lamellar austenite grains with the mean lamellar spacing of 230nm. The martensite transformation starting (Ms) temperature decreased with increasing the ARB strain. The nano-martensite transformed from the UFG austenite showed characteristic morphologies and performed very high strength up to 970MPa.
