Development of Texture in Ultrafine-Grained Low-Carbon Steel Processed through Equal-Channel Angular Pressing

Abstract

Developments of microstructures and texture are investigated for a low-carbon steel deformed by equal-channel angular pressing (ECAP) at room temperature for equivalent strain (evm) of 16.8. ECAP at evm = 0.6 reduces grain size by two orders of magnitude. With increasing strain, grain size reduces further and high-angle grain boundary (HAGB) fraction improves by grain subdivision and its change in orientation. ECAP of low-carbon steel up to evm = 16.8 can produce ultrafine grains of 0.2 µm size with HAGB fraction of 82%. The as-received steel has low texture index. Microstructural changes strongly influence texture development. It increases with equivalent strain as grain subdivision continues. Texture index fluctuates at intermediate strain range due to randomization of initial texture. Texture index reaches saturation at the high equivalent strain. On ECAP at low to intermediate strain evm = 0.6-6, components of both α (Fθ, Jθ, and $$ \overline{J} $$ θ) and γ (D1θ, D2θ, and Eθ) fibers are developed though all of them deviate from their ideal positions. At higher strain (evm = 9-16.8), the γ fiber components (D1θ, D2θ, Eθ) are strengthened, and the Eθ component reaches the highest intensity of ≈ 17 at evm = 12. There is no texture symmetry at low to high strain level. The presence of pearlite in low-carbon steel enhances strongly the deviation of texture components from their ideal positions in Euler’s space as well as it increases the intensities of the components more than that of IF steel for a similar equivalent strain.