Analysis of through-thickness heterogeneities of microstructure and texture in nickel after accumulative roll bonding

The through-thickness heterogeneities of the microstructure and texture have been investigated in pure nickel processed by six cycles of accumulative roll bonding (ARB) with lubrication applied during each rolling pass. Strong rolling textures are found in the intermediate and center layers of the deformed sample, whereas increased fractions of the shear texture are observed near the surface. Significant differences at different depths are also revealed in the fractions of areas containing either predominantly low angle misorientations or predominantly high angle misorientations. It is found that the fractions of such areas are much more sensitive to the deformation history than the average parameters based on the measurements of the boundary spacing and fractions of high angle boundaries. For the material studied in this work, the area fraction of the low misorientation regions appears to correlate with the summed fraction of the rolling texture components. The observed microstructural and textural variations are discussed and compared with literature data, taking into account the influence of large-draught rolling and lubrication on the distribution of strain imposed during the ARB process.