Tensile-relaxation behavior of electrodeposited nanocrystalline Ni

Abstract

The electrodeposited nanocrystalline (nc) Ni with an average grain size of 27 nm by the tensile-relaxation tests shows substantial increase in ductility up to 10.7%–11.8% at all tested strain rates (from $4.17\times {10}^{-5}$ to $4.17{\text{s}}^{-1}$ ), which is evidently higher than those (6%–10%) attained in the routine continuous tensile tests; while the ductility of the compared coarse-grained (CG) Ni almost keep invariable under the same two kinds of tension mode. Additionally, the notable stress softening and the subsequently parabola of convergence increase in flow stress (i.e., new strain hardening behavior) upon reloading was only observed in nc Ni during the tensile-relaxation tests, which illuminates that nc Ni lacks a permanent dislocation network like that in CG Ni during deformation process.