Taichi Kamijo

Development of cube texture in aluminum single crystals of a stable orientation

Abstract Aluminum single crystals in a stable (348)[ 11 4 6] orientation for rolling were cold-rolled up to 99% under two series of L/d conditions. The effects of rolling geometry on the formation of nucleation sites and on the development of cube texture were investigated. The formation of a cube texture with good symmetry was confirmed in aluminum single crystals. The results obtained were attributed to the preferential nucleation from the (001)[100] deformation structure formed during rolling due to deformation inhomogeneity.

Nucleation and growth of cube-oriented recrystallized grains in an aluminum single crystal of an s-orientation

Abstract In order to elucidate the formation of the cube texture, an aluminum single crystal in a (348) [ 11 , 4 , 6] orientation was cold-rolled to 99% and annealed at various temperatures. Microstructural observations with an optical microscope and texture measurements revealed that the nuclei of the cube grains were preferentially formed within band-like structures, which originated during cold-rolling. Several fine grains located 20–50 μm within the sheet surfaces became larger pancake-shaped grains lying parallel to the rolling direction. These recrystallized grains grew rapidly into the middle of the sheet before nucleation at shear bands. Very coarse (001)[100] grains through the sheet thickness were developed at higher temperature.

Formation of a (001)[100] deformation structure in aluminum single crystals of an S-orientation

Abstract Generation of a (001) [100] deformation structure to be preferential nucleation sites of a cube texture was clarified in aluminum single crystals of an S-orientation cold-rolled up to 99%. The orientation spread heading for the formation of symmetrical components of the initial (348) [ 11,4 6] orientation was increased and the ( 1 ,2,14)[ 21 0] intermediate component was produced due to deformation inhomogeneity after 80% cold-rolling. The slip rotation of the minor part of material in the ( 1 2,14)[ 21 0] orientation around the normal direction should be responsible for the formation of the (001)[100] deformation structure during subsequent rolling.

Formation of cube texture in copper single crystals

Abstract The rolling and the recrystallization textures of the copper single crystal in the stable (123) [ 63 4] orientation were studied, so as to clarify the origin of cube texture. The sharp original (123) [ 63 4] component was maintained in the crystals cold-rolled up to 95%, but the orientation spread suggesting the occurrence of slip rotation toward a symmetrical component of (321)[ 4 36] was observed. The formation of the cube-oriented deformed material, which provided available nucleation sites of cube texture, was confirmed in the crystals cold-rolled more than 99%. The deviation from the stable orientation and the slip rotation toward (001)[100] might be triggered by inhomogeneous deformation during rolling. The recrystallization texture composed of the (001)[100] orientation with large scatter and the retained rolling texture component was formed in the crystal cold-rolled 95%. The cube texture was developed with increasing rolling reduction.

Formation of texture during high temperature deformation of Ti-50·3 mol.% Al

Abstract Ti-50·3 mol.% Al was deformed in compression under various conditions. Texture as well as microstructure in the dynamically recrystallized state were investigated. One-to-one correspondence existed between the size of dynamically recrystallized grains and the peak stresses appearing in stress-strain curves. Formation of a fiber texture was confirmed. The texture developed with a decrease in peak stress. Extensive occurrence of strain-induced grain boundary migration was observed in the initial stage of dynamic recrystallization at the deformation conditions where sharp textures were formed after large deformation. Measurement of {021) pole figure suggested that the main component of the fibre texture was located between {011) and {021) (compression plane).

Inhomogeneous deformation in embedded aluminum single crystals during cold-rolling

In order to clarify the formation mechanism of the (001)[100] deformation structure and the complementary component, aluminium single crystals in the stable C and D as well as unstable (115)[552] orientations were cold-rolled in the constraining frames to 55, 80 and 90%. Two orientation changes C → D → (001)[110] → D → Cand D → C → (111)[112] → G appeared around the transverse direction. Material flow in the embedded crystals during rolling was quite irregular. The slip rotation toward unstable orientations from the stable C or D and the large spread around the initial orientations might be attibuted to deformation inhomogeneity, caused by the inclination of stress system in rolling due to reaction given by the constraining frames.

A nucleation theory of homogeneous precipitation triggered by fluctuation of composition

Abstract The free energy barrier to be surmounted during nucleation in homogeneous coherent precipitation of a new phase is discussed in terms of nucleation triggered by the fluctuation of composition. An equation describing the free energy change of a system attending the formation of a solute-rich cluster or a new phase in a dilute regular solution is derived. The curved surface showing the free energy barrier is drawn using the equation and the interaction enthalpy obtained in a previous paper (Kamijo and Fukutomi 1983). The critical size and composition of the solute-rich cluster or the nucleus as well as the critical values of free energy change are evaluated by means of analysis of the curved free energy surface. The mutual relationship between the theories proposed by Becker (1938, 1940), Hobstetter (1949) and Borelius (1937) is discussed and the nucleation process triggered by the fluctuation of composition is clarified.

The numbers of critical nuclei and embryos for coherent precipitation of a new phase of different composition

Abstract The increase in free energy which accompanies homogeneous nucleation, the number of atoms contained in the critical nucleus and the concentration of nuclei formed during coherent continuous precipitation in a dilute regular solution, as well as their temperature dependences, are discussed on the basis of a statistical-thermodynamic approach. A theoretical equation describing the relationship between the concentration of small atom groups and the change in configurational entropy is proposed and developed, so as to evaluate the numbers of nuclei and embryos with equilibrium size distribution, by introducing the enthalpy change due to the decrease in the number of atomic bonds between unlike atom.