Nanocrystalline steel processed by severe rolling of lath martensite

Nanocrystalline steel was developed by severe cold-rolling and subsequent annealing of low carbon steel with an original microstructure of lath martensite. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that steel with an average grain size of −20 to −300 nm can be obtained. The tensile tests revealed that the steel with grain size of −20 nm possess a strength of 2520 MPa and poor ductility at ambient temperature.