Investigation of Hot Workability and Microstructure Evolution of VGCNFs-Reinforced Aluminum Matrix Composites

Isothermal compression experiments of vapor-grown carbon nanofiber (VGCNF)-reinforced aluminum matrix (VGCNF/Al) composites and pure aluminum (Al) were conducted at deformation temperatures from 573 K to 723 K and strain rates from 0.01 to 1 s^-1. It was found that the VGCNF/Al composites and pure Al had depressed dynamic recrystallization percent in the high-power dissipation efficiency regions. Upon　comparing the processing maps for different strains, it was found that the high-power dissipation efficiency regions of the VGCNF/Al composites and pure Al moved from the low strain rate region to the high strain rate region. The kernel average misorientation images showed that there were lots of low-angle grain boundaries in the high strain rate region. The low-angle grain boundaries did not have enough time to transform into high-angle grain boundaries, resulting in a depressed percentage of dynamic recrystallization. The addition of VGCNFs led to an increased low-angle grain boundary density. As a result, the phenomenon of high-power dissipation regions in the high strain rate regions correspond to the low percentage of dynamic recrystallization was more obvious.