Orientation Relationship for Fine Grains Formed by Diffusion-Induced Recrystallization in the Ni(Cu) System

Abstract

In order to examine the crystallography for diffusion-induced recrystallization (DIR) in the Ni(Cu) system, Cu/Ni/Cu diffusion couples were prepared by a diffusion bonding technique from a pure Cu single-crystal specimen and a pure Ni polycrystalline specimen, and then isothermally annealed at a temperature of 923 K for various times of 1–60 h. The Miller indices of the Cu specimen along the Cu/Ni interface are (111). The notation A(B) means that a solute B diffuses into a pure metal A or a binary A–B alloy with the A-rich single-phase microstructure. Due to DIR during annealing, a region with fine grains alloyed with Cu is produced into the Ni specimen from the Cu/Ni interface in the diffusion couple. The orientation relationship between the fine grain in the DIR region and the Cu or Ni specimen was analyzed by an electron backscattered diffraction technique as well as transmission electron microscopy. Orientation relationships close to but not identical to the cube/ cube relationship exist between the Cu specimen and many fine grains in the DIR region. The chemical driving force for the formation of the DIR region, the boundary energy and the boundary diffusion coefficient were evaluated by mathematical models. According to the evaluation, it is likely that fine grains surrounded by small-angle boundaries are formed and grow moderately during DIR. [doi:10.2320/matertrans.MRA2007197]