U. Chakkingal

Bio: U. Chakkingal is an academic researcher from Rensselaer Polytechnic Institute. The author has contributed to research in topics: Recrystallization (metallurgy) & Die (manufacturing). The author has an hindex of 1, co-authored 1 publications receiving 18 citations.

The evolution of annealing textures in 90 Pct drawn copper wire

Abstract: An electrolytic copper rod was drawn in 24 passes to a 90 pct reduction in area and subsequently annealed under various conditions. The global texture of the drawn wire, as measured by X-ray methods, showed a fiber texture approximated by a strong 〈111〉 and a weak 〈100〉 component. However, its microtexture, as measured by electron backscattered diffraction (EBSD), indicated that the major 〈111〉+minor 〈100〉 duplex fiber texture was dominant only in the center region, while a relatively diffuse texture developed with a somewhat higher density of orientations having a 〈11w〉//wire axis in the middle and surface regions. The inhomogeneous texture in the as-deformed wire gave rise to an inhomogeneous microstructure and texture after annealing. When annealed at 300 °C or 600 °C for 3 hours, the wire developed a duplex fiber texture consisting of major 〈100〉+minor 〈111〉 components in the center region, a strong 〈100〉 fiber texture in the middle region, and a weak texture consisting of 〈111〉 and 〈100〉 components with the 〈111〉 component being slightly stronger in the surface region. When the drawn wire was annealed at the high temperature of 700 °C, the texture at short annealing times was similar to that of the wire annealed at the lower temperatures of 300 °C and 600 °C for 3 hours, but prolonged annealing gave rise to a texture ranging from the 〈111〉 to 〈112〉 components due to abnormal grain-growth that started in the surface region. The recrystallization texture consisting of the major 〈100〉+minor 〈111〉 components was explained by the strain-energy-release maximization (SERM) model, in which the recrystallization texture is determined such that the absolute maximum principal stress direction due to dislocations in the deformed state is along the minimum elastic-modulus direction in recrystallized grains. On the other hand, the abnormal grain-growth texture was attributed to grain-boundary mobility differences between differently oriented grain.

Characterization of microstructure evolution after severe plastic deformation of pure copper with continuous columnar crystals

Abstract: Pure copper bar with continuous columnar crystals was fabricated by continuous unidirectional solidification. The bar with orientation preference along [0 0 1] exhibited novel plastic deformation ability with total true strain over 13.5 during rolling and drawing at room temperature without annealing. Microstructure analysis and in situ observation of tensile test were performed to investigate the mechanism of plastic deformation. Results exhibit that the novel plastic deformation ability of copper bar is beneficial from the absence of transverse grain boundary as well as small angle grain boundary of the continuous columnar microstructure. The existence of cell structure, recrystallization and deformation twin leads to grain rotation during deformation and enhances the orientation preference of the continuous columnar crystals, enabling copper bar a high ability for further deformation.