Flat products of carbon nanotubes (CNTs) reinforced Al matrix composites were fabricated using flake powder metallurgy via shift-speed ball milling and hot-rolling. The evolution of CNTs during preparation and the final distribution in the Al matrix were investigated, and the effect of CNT content on mechanical properties were discussed. Due to the combined effect of uniform dispersion of CNTs, structural integrity, interfacial bonding and directional alignment, the balance between high strength and ductility was successfully achieved in the annealed rolled composites with 1.5 wt% CNT addition, with the value of 382.6 MPa in tensile strength and 9.8% in fracture ductility. The load transfer strengthening was the main mechanism of the strength enhancement with CNTs addition. In addition, a strong rotated cube {001}〈110〉 texture was found in the final flat product of rolled composites. This study provides an effective route to produce and improve the mechanical properties of CNT/Al flat products.

Aluminum matrix composites were prepared by powder processing route containing three different loadings of graphene nanoplatelets, i.e., 1 wt%, 3 wt%, and 5 wt%. Ball milling of composite powders was performed to ensure the uniform dispersion of nanoplatelets in aluminum powder, followed by their consolidation to near theoretical densities. Microstructural evolution after composite preparation was witnessed by X-ray diffraction, optical microscopy, and scanning electron microscopy, while the mechanical property profile was evaluated by hardness, compression, and flexural tests. The mechanical properties of composites containing 5 wt% nanoplatelets were found with maximum improvements in hardness, compression, and flexural strengths of 35%, 433%, and 283%, respectively. This increase in mechanical performance is related to uniform dispersion and microstructural development in composites by incorporating nanoplatelets. Fractographic characterization indicated a change in fracture morphology from matrix-dominant in pure aluminum to nanoplatelet-dominant in composites. In particular, shearing and pull out of nanoplatelets were observed during the fracture of composites with simultaneous restricted plastic deformation of the surrounding aluminum matrix.

Semisolid forging is a type of semisolid metal processing with high solid fraction. However, the presence of nanosized particles has strong influences on flow behavior of the composites in the semisolid forging process. In this study, the compression deformation behavior of nanosized Al2O3 particles (Al2O3np) reinforced 7075 aluminum matrix composites with high solid fraction was investigated by conducting semisolid isothermal compression experiment. The microstructures after semisolid compression were characterized. The results showed that the true stress decreased with the increase of the deformation temperature and size of Al2O3np, the decrease of the strain rate and mass fraction of Al2O3np. After semisolid compression, deformation degree in large deformation zone was larger than that in free deformation zone. Besides, the solid grains in large deformation zone showed evidence of having undergone different degrees of plastic deformation under different deformation conditions. Simultaneously, the deformation mechanisms during the semisolid compression process were discussed.