The role of orientation pinning in statically recrystallized oxygen-free high-conductivity copper wire

Abstract

The role of orientation pinning by neighboring grains on migrating boundaries in a statically recrystallized oxygen-free high-conductivity (OFHC) copper was investigated. Two specimens of heavily drawn OFHC copper wires deformed to true strains of 2.31 and 3.56 were annealed at 170 °C and local orientations were mapped by means of the automated electron backscattered diffraction technique. Inverse pole figures, misorientation distribution functions, and grain boundary misorientations were calculated from local orientation data. In spite of annealing, the microstructure of the low-strain specimen was characterized by elongated grains, similar to the as-deformed structure, whereas the microstructure of the high-strain specimen showed a high fraction of well-defined recrystallized grains. The recrystallized grains consisted of type A grains, which mostly grew laterally with {hkl}Ͻ100Ͼ orientations, and type B grains, which generally grew axially with {hkl}Ͻ111Ͼ orientations. Type A grains were larger and of higher frequency than type B grains. The large size of Type A grains was attributed to the high frequency of the mobile boundaries with misorientations in the 40 to 50 deg range. Boundaries that were misoriented at 60 deg Ͻ111Ͼ (⌺3) were found to exert the greatest pinning effect on the growing grains. This caused recrystallized grains to grow either laterally or axially, and sometime led to "branching." A detailed analysis of the influence of the next neighbor misorientations in the perimeter of the recrystallized grains is presented.

Microstructure and microhardness of OFHC copper processed by high-pressure torsion

“…This was attributed to the easier dislocation movement in the high purity steel leading to greater grain boundary mobility and a higher probability of twin boundary generation. Similarly, an investigation of the role of orientation pinning by neighboring grains on migrating boundaries in a statically recrystallized OFHC copper showed that some recrystallized grains with Σ3 boundaries exerted the greatest pinning effect on the growing grains [63]. Adopting a similar analogy in the present experiments, it is proposed that the low mobility of the Σ3 boundaries, which are formed by dynamic recrystallization in the early stage of HPT straining, produces a resistance to excessive grain growth of the recrystallized grains and therefore the material becomes susceptible to dislocation accumulation followed by subgrain formation with additional shearing.…”

Influence of deformation inhomogeneity on the annealing behavior of drawn oxygen-free high conducting copper

“…Type A grains were mostly oriented at ,100.//DD and were larger and of higher frequency than type B grains, which generally had a ,111.//DD orientation. In a separate study of these two types of grains, 16 the large size of type A grains was attributed to the high frequency of the mobile boundaries with misorientations in the 40-50°range, and boundaries that were misoriented at 60°,111. (twin boundaries, R3) were found to exert the greatest pinning (retarding) effect on the growing grains.…”

“…A detailed analysis of the grain boundary characteristics and their influence on the recrystallization of the two types of grains has been reported elsewhere. 16 Size distribution and microtexture: Fig. 9 shows distribution of type "A" and type "B" grains in terms of the inclination angle b.…”

Investigation of recrystallization and grain growth of copper and gold bonding wires

“…This will be discussed further in Section IV. It is also notable that the second stage of discontinuous recrystallization clearly nucleates in the subsurface region and spreads to the rest of the cross section, as observed by Waryoba et al [29] The as-deformed copper wire of 25-mm diameter has both ,111. and ,100. fiber components. During annealing, texture and microstructure change.…”