Experimental study of the effects of annealing time, equilibrium angle, and absolute misorientation angle on thermal grain-boundary groving in cube- texture nickel

摘要

Several technical problems are associated with the rolling-assisted biaxially-textured substrates (RABiTS) method of fabricating long lengths of high-temperature superconducting wire. For example, controlling or eliminating thermal grain-boundary groove defects on the Ni base layer of the substrate is an important concern. Thermal grooves on the surface of the Ni may have the potential to cause cracks or growth defects to form in the buffer and superconducting layers which are epitaxially deposited on the Ni. Thus, the effects of annealing time, equilibrium angle, and absolute misorientation angle on thermal grain-boundary grooving in cube-textured nickel were investigated. Small samples of RABiTS Ni were recrystallized at 800 C for times of 10, 30, 60, and 120 minutes to produce diffusion-induced thermal grooves on their surfaces. The linear dimensions and equilibrium angles these grooves were measured using atomic force microscopy. The misorientations of grains at triple point junctions were measured using electron back-scatter diffraction, and the cube-texture of the samples was analyzed with x-ray diffraction. Grain size measurements were also made on each sample. The linear dimensions of grooves evolved with annealing time in accordance with Mullins' theory of thermal grooving. Average groove depths increased with increasing equilibrium angle; however, there was only a slight tendency for groove depth to increase with increasing absolute misorientation angle. In general, groove depths did not exceed 650 (angstrom). The cube texture and grain size of the samples were typical of RABiTS Ni.