Microstructure evolution and strength-ductility improving mechanism change of heterogeneous CNT/2009Al composite after hot rolling

In this study, heterogeneous carbon nanotubes reinforced 2009Al (CNT/2009Al) composites composed of CNT-free ductile zones (DZs) and CNT-rich brittle zones were prepared by powder metallurgy , followed by hot extrusion and hot rolling. For the extruded heterogeneous composite (Hetero-C), its strength was increased by about 30 MPa with a more than 1/3 elongation increase, as compared with those of the uniform composite. After hot rolling, the two zones of the heterogeneous composite (R-Hetero-C) were much narrower than those of the Hetero-C, which was not beneficial to increase elongation. However, the texture analysis demonstrates that the Hetero-C had a< 111 > fiber texture, while the R-Hetero-C had strong plate textures including {011}< 111 > , {113}< 332 > and {215}< 342 > components. These plate textures with high Schmidt factor induced more matrix grains to participate in plastic deformation at relatively low stress, which could enhance the elongation but slightly reduce the strength. The synergy of these two different aspects led to the slightly reduced yield strength, similar ultimate tensile strength, and increased elongation for the rolled heterogeneous composite, as compared with those of the extruded heterogeneous composite.