Novel interface characteristics and strengthening mechanisms in extruded fiber(Ti)-reinforced Al-based composites

Abstract

Tailoring Al/Ti composites with high toughness and tensile plasticity requires a comprehensive understanding of multi-scale interface microstructures and element diffusion behaviors. In this study, Al/Ti composites are produced by a novel continuous extrusion technique. Interfacial microstructures, elemental diffusion, and mechanical characteristics are systematically investigated using up-to-date electron microscope technology. The interlayer thickness grows from 0.8 to 4.2 µm when the annealing duration is increased from 6 to 48 h. The interlayer growth behavior exhibits a mixed reaction–diffusion process and is dominated by the interfacial chemical reaction. Elements Si and Mg are aggregated at the Ti/TiAl3 and Al/TiAl3 heterogeneous interfaces, respectively, where the diffusion of Al and Ti is inhibited. A gradient structure at the interface is generated via severe thermal and mechanical effects during extrusion, including fine Ti grains, superfine Al grains, and coarse Al grains. Deformation-induced dislocations and nanograins are observed near the welding interface. Micro-scale interlocking and nano-scale intermixing structures are formed under strong welding pressure. Compared with the conventional Al bar, the ultimate tensile strength and plasticity of the extruded composite Al bar are enhanced by 5.7% and 32.2%, respectively. This work provides new strategies for developing Al/Ti composites with exceptional strength and ductility.