Yindong Shi

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

ABSTRACT 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.

Formation processes of dislocation cells in cryorolled Zr upon annealing

Abstract In the present study, the formation process of dislocation cells in cryorolled Zr has been studied. High density dislocations were introduced into pure Zr by employing cryorolling technique. Dislocation lamellas are yielded in cryorolled Zr at a high strain rate of  = 2·24 s−1, and these lamellas fragment or bend into dislocation cells during annealing processes. Instead, in the cryorolled Zr yielded at a low strain rate of  = 0·59 s−1, dislocation cells form by the fragmenting or the necking of dislocation tangle regions. The formation process of dislocation cells in cryorolled Zr is dependent on dislocation configurations induced in the metal.