High Strength and High Uniform Ductility in a Severely Deformed Iron Alloy by Lattice Softening and Multimodal-structure Formation

Despite high strength of nanostructured alloys, they usually exhibit poor uniform ductility. For many applications, it is an important issue to design new nanostructured alloys which have both high strength and high uniform ductility. In this study, an Fe-Ni-Al-C alloy with ultrahigh tensile strength of 1.9-2.2 GPa and high uniform ductility of 16-19% was developed by concurrent employment of several strategies: (i) appropriate choice of chemical compositions for lattice softening, (ii) severe plastic deformation using the high-pressure torsion method for grain refinement, and (iii) control of strain level for multimodal-structure formation composed of equiaxed nanograins, lamellar coarse grains and fine precipitates.