Effect of Initial Grain Size on the Evolution of {001}〈100〉 Texture in Severely Deformed and Annealed High-Purity Nickel

Abstract

Development of cube texture ({100}〈001〉) was studied in high-purity Ni (99.97 pct) with widely different starting grain sizes (~28 and 650 μm) following ultrahigh straining (eeq = 6.4) by accumulative roll bonding (ARB) and annealing. The fine-grained starting material (FGSM) develops a much stronger cube texture after different annealing treatments as compared to the coarse-grained starting material (CGSM), despite their very similar bulk deformation texture. A lamellar type deformation structure is observed in both these materials, but the CGSM shows a more fragmented structure and frequent presence of shear bands. The recrystallization texture of the two materials differs right from the onset of recrystallization: cube-oriented grains nucleate and grow in the FGSM in sharp contrast to the nucleation and growth of randomly oriented grains in lamellar as well as shear-banded regions of the CGSM. The observed differences in the evolution of recrystallization texture in the two materials are discussed with regard to the microstructural differences and pertinent theories on the formation of cube texture.