Study On Microstructure And Properties Of Electrodeposited Nickel With Cold Rolled And Annealed

Electrodeposited nickel materials are widely used in machinery, automotive,instruments and other industry areas. The initial texture and grain morphology willaffect the formation of deformation texture and recrystallization texture, thus theproperties of the material. Little research was carried out on the electrodepositednickel materials. In this paper, the electrodeposited coarse-grain nickel-plate andsub-micrometer-grained nickel foil，the raw materials, experienced the cold rollingand annealing treatment. The microstructure and properties of the coarse-grained andsub-micrometer-grained nickel of rolled and annealed state were analysed by XRDDiffraction, Optical Microscopy, Micro-hardness, Electron Backscattered Diffraction(EBSD). The deformation texture and recrystallized texture evolution ofcoarse-grained and sub-micrometer-grained nickel were compared. The effectmechanisms of the different initial texture and grain morphology on deformationtexture and recrystallization texture were explored, the research is of significance forthe texture control and mechanism of plastic deformation. The results were asfollows:(1) Samples with different initial texture (with the deposition surface to0°,30°,45°,90°) got the {220} cold rolled texture after70%cold deformation; Themicrohardness of rolling surface of original coarse-grained nickel declined with theincrease of initial cutting angle, which resulted from the transverse grain boundariesof the sample decreased with the increase of initial cutting angles. The cold rollingcaused work hardening, so the micro-hardness increased significantly. Moreover, thetrend of micro-hardness remained decreasing with the increase of initial cuttingangles. Unlike coarse-grained nickel, sub-micrometer-grained Ni achieved strong{200} texture after20%cold rolled deformed, and its texture coefficient reached0.9379; The micro-hardness was not change too much, and the work hardening wasnot obvious.(2) The annealing treatment of coarse-grained and sub-micrometer-grainednickel of rolled state were carried out at400°C. The XRD results showed that, the 20%deformed sample of coarse-grained nickel cutting from0°remained the initialcold-rolled {220} texture after annealing, and its texture coefficient was0.6476. The70%deformed sample of coarse-grained nickel cutting from0°got weak {200}recrystallization texture after annealing, and its texture coefficient was0.4040.Meanwhile, the coefficient of cold-rolled {220} texture, which partly remained, was0.4380. Different with coarse-grained nickel at the same condition, thesub-micrometer-grained nickel with20%cold deformation got weak {200} and {111}texture after annealing. Their texture coefficient were0.3913and0.38850, and thepreferred orientation was not obvious.(3) The microstructure evolution of the undeformed and deformedsub-micrometer-grained nickel were compared. The original sub-micrometer-grainednickel remained the initial {100} fiber texture and microstructure after annealing at400°C, its cross-sectional shape remained the columnar crystals, and the surfaceshowed the non uniform equiaxed grains; When annealing time was15min, a smallnumber of abnormal growth grains appeared in the surface. Thesub-micrometer-grained nickel with20%cold deformation got weak Cube {100}<001> after annealing. Recrystallization mechanisms of sub-micrometer-grainednickel was proposed: deformed specimens first nucleated on the boundaries ofdeformation twins during annealing, with the increase of annealing time, high anglegrain boundary occured migration, and replaced the small-angle grain boundaries.The recrystallization core grew, then in both of its cross-sectional shape and surfaceof the sub-micrometer grained, the equiaxed grains formed.