Mechanical anisotropic behavior of low-carbon steel processed by asymmetric rolling.

In the present work, the mechanical anisotropic behavior of low-carbon (Fe-0.07C) steel processed by asymmetric cold rolling was investigated. Three different types of dynamic recrystallization (DRX) mechanisms (continuous, discontinuous, and geometric) were observed in the microstructure of the 75 % cold-rolled sheet. The average intensity of γ-fiber was remarkably enhanced to 2.8 × R as rolling deformation increased to 50 % due to the formation of many deformation bands. After 75 % cold rolling, the average intensity of γ-fiber was significantly decreased to 1.4 × R due to the creation of new recrystallized grains. The results exhibited that the hardness of the low-carbon steel sheet was 260.1 HV by 75 % cold rolling, which was 1.75 times larger than the initial low-carbon steel sheet. With increasing deformation degree, the average yield and tensile strengths gradually improved and reached a peak value of 844.8 MPa and 881.7 MPa after 75 % cold rolling, respectively, which were 2.8 and 2.1 times that of the initial low-carbon steel sheet. By increasing the rolling reduction up to 50 %, the mechanical anisotropy gradually enhanced and by further increasing the cold deformation to 75 %, the anisotropy rapidly decreased due to the weakening of the γ-fiber texture. The strength was the highest along the transverse direction (90°) in all low-carbon steel sheets, and decreased at 0° and 45°. The dσ/dε-ε curves of the 50 % cold-rolled low-carbon steel sheet for the 45° and 90° tensile directions exhibited two distinct stages during the loading, however, that for the 0° revealed only one stage. A large number of parallel striations were present on the fracture surface of the 50 % deformed low-carbon steel sheet at 90° due to the presence of parallel deformation bands.