Enhancing the mechanical properties of low-carbon steel by a graded dislocation microstructure

In the present paper, the microstructures and mechanical properties of a low-carbon steel processed by graded pre-torsion (PTO) and homogeneous pre-tension (PTE), respectively, have been investigated. Experimental results demonstrate that both PTO and PTE can improve the strength of the low-carbon steel, but at a loss of ductility and toughness. However, a much better strength–ductility–toughness synergy is achieved in samples processed by graded PTO than that in samples subjected to PTE. This enhancement of comprehensive mechanical properties is due to the formation of a graded microstructure, that is, the dislocation-density increases gradually with decreasing the depth from the sample surface. This study provides a strategy for enhancing the mechanical properties of metallic materials by graded plastic deformation.