Grain Orientation Induced Softening in Electrodeposited Gradient Nanostructured Nickel during Cold Rolling Deformation

Abstract

Quantitative microstructural evolution and the corresponding microhardness of electrodeposited nanostructured nickel sheet during cold rolling deformation are investigated by x-ray diffraction, transmission electron microscopy and Vicker’s microhardness testing. Particularly, to investigate the effect of stress states on deformation behavior, two series of gradient nanostructured nickel with symmetric structures and the homogeneous counterparts with three levels of grain size are compared based on macro-statistical data. In such hierarchical sandwich-like gradient samples, the layers with larger grain size, as the soft phase, indeed sustain more deformation. Deformation-induced grain rotation changes are observed in the center layers with a relatively larger grain size, accompanied by an obvious decrease in microhardness. According to the quantitative microstructural parameters including the grain size, dislocation density and stacking fault probability before and after deformation, evaluation based on Hall-Petch and Bailey-Hirsch relationships indicates the transition from strain hardening to softening can be attributed to grain orientation change.

Strain dependent grain growth during cold rolling deformation of gradient nanograined nickel

“…Two groups of gradient nanograined nickel samples with symmetrical structure were prepared by electrodeposition following the procedure described in the previous literature [9], except for electrodeposition time at given current density varying 1.5~15A/dm2. Rolling deformation was conducted to achieve similar nominal rolling strain reported in our previous publication [8].…”

“…For the electrodeposited homogeneous nanograined nickel, it is generally accepted that larger grains typically tend to deform via full dislocations, whereas smaller grains typically tend to deform via partial dislocations [6][7]. In light of this, our previous work on the rolling deformation of grain-size gradient nanograined nickel has preliminarily reported microstructure evolution and the corresponding microhardness variation of several typical layers with different grain size levels [8]. However, the volume fractions of the typical layers in the two samples are different.…”

Dead Lithium in Lithium Metal Batteries: Formation, Characterization and Strategies

“…Compared with Li 2 CO 3 , the main component in natural SEI, LiF can reduce the energy barrier of Li + diffusion in SEI, induce uniform Li + deposition, and inhibiting the formation of Li dendrites. [53][54][55] Up to now, there are many methods to inhibit Li dendrites, including composite anodes, [56][57] which are based on carbon framework/conducting polymer main body, [58][59][60][61][62] lithiophilic doping, [61] separator modification, [62][63] using electrolyte additives, [64][65] etc., they were used either to create conditions for uniform Li deposition to use SEI and separator to control the growth of Li dendrites. [52] It is noteworthy that some strategies to inhibit the growth of Li dendrites also should take into account the ionic conductivity, which also have a direct effect on eliminating dead Li.…”