Effect of bimodal microstructure on texture evolution and mechanical properties of 1050 Al alloy processed through severe plastic deformation and subsequent annealing

摘要

In this study, aluminium sheets were processed through 8 cycles of accumulative roll bonding (ARB), and then, were annealed at 300 °C for different time periods to maintain the optimum annealing process for the formation of bimodal microstructure. Variations in microstructure, texture, and mechanical properties were studied using optical microscopy (OM), X-Ray diffraction (XRD), and hardness and uniaxial tensile tests. Microstructural observations showed that recrystallized grains formed after 10 s of annealing; however, recovery occurred after 1 s due to the high stacking fault energy (SFE) of aluminium. Fully recrystallized microstructure was seen after 900 s. A bimodal grain size was achieved after 3600 s and the ratio of the average size of the largest 2% grains to mean grain size (d_(max)/) was 3. Abnormal grain growth took place with the increasing of annealing time to 18,000 s during which the d_(max)/ ratio reached 7. During annealing, Copper, Dillamore and S components remained the main texture components; however, their intensity reduced with increase in annealing time. In addition, the Cube component formed after the cessation of recrystallization and abnormal grain growth. After 18,000 s of annealing, ultimate tensile strength (UTS) decreased more than 70% and elongation increased 230%; however, the maximum toughness was achieved in the sample annealed for 3600 s. Formation of a bimodal grain size microstructure with d_(max)/ ratio of 3 was the main reason for this phenomenon.