Influence of structural heterogeneity on the structural coarsening during annealing of polycrystalline Ni subjected to dynamic plastic deformation

The structural heterogeneity of a polycrystalline Ni subjected to dynamic plastic deformation to a strain of 2.3 was characterized, and its influence on the structural coarsening behaviour during post annealing was investigated. Structural heterogeneity on the large scale manifests itself by formation of two types of layers: low misoriented regions (LMRs) and highly misoriented regions (HMRs). On the small scale, the heterogeneity was characterized by different distributions of boundaries and textures in each layer. LMRs contain only low angle boundaries and one dominating crystallographic orientation. In contrast HMRs contain both low and high angle boundaries (>15) and the texture is mixed with <011> close to the compression axis. During annealing, LMRs coarsen uniformly and recrystallization nucleation is difficult to form. In HMRs, the structural evolution is heterogeneous and recrystallization nuclei are readily formed. The importance of structural heterogeneity during structural design for high performance nanostructure was highlighted.