Hot deformation behavior and processing maps of hybrid SiC and CNTs reinforced AZ61 alloy composite

Abstract

The hot deformation behavior of hybrid SiC and CNTs reinforced AZ61 alloy composite was investigated by hot compacting at the strain rate range of 10−4–0.1 s−1 and temperature range of 250–400 °C. The constitutive equation and processing maps were successfully established and checked. The results revealed that the composite exhibited typical flow behavior of metallic materials, and the flow stress increased as the temperature decreased and strain rate increased. The flow behavior was precisely described by using hyperbolic sine constitutive equation in this work. The average stress exponent and activation energy of the composite are 4.9 and 174 kJ/mol, respectively, indicating that the dominant deformation mechanism might be dislocation climb. The processing maps of the composite exhibited two instability zones and two safe zones (250–330 °C, 0.001–0.006 s−1 and 350–390 °C, 0.0001–0.0005 s−1) for selection of optimum processing parameters. Dynamic recrystallization (DRX) occurred in the safe zones, however, cracking and twinning were observed in the instability zones. In addition, the examination of microstructure evolution revealed that DRX gradually occurred more adequately as the temperature increased and strain rate decreased, and SiC particulates could promote the DRX of the composite due to the particle stimulating nucleation (PSN) effect.