純ニッケルの動的再結晶における集合組織形成の組織学的検討

抄録

Nucleation mechanism from initial grain boundaries and the process of texture formation during dynamic recrystallization in pure nickel were studied in uniaxial compression tests at temperatures of 293 K, 873 K and 905 K and true strain rates of 1.0×10⁻³ s⁻¹ and 1.0×10⁻⁴ s⁻¹. Microstructures were observed by optical microscopy and SEM. Orientation measurements of individual grains were carried out by EBSP technique. Misorientation between neighboring points along grain boundaries in the specimen deformed at high temperature having wavy grain boundaries were greater than that in the specimen deformed at room temperature having smooth grain boundaries. Further, the misorientation was larger when the degree of grain boundary curvature was more severe. These indicate that vicinity of wavy grain boundaries is the region of inhomogeneous deformation. These regions have various orientations locally because of lattice rotation to various directions. New grains nucleated from these regions had almost random orientation. At high Zener-Hollomon parameter conditions, area of high pole density was distributed about 10 degrees away from (011) to (001). The reason is as follows; at fully dynamically recrystallized material, new grains nucleate with random orientation, followed by the orientation change towards (011) by the deformation. Before some grains reach to (011), however, new grains nucleate again with random orientation and grains with (011) orientation disappears.