Multiscale microstructures, mechanical properties and electrical conductivity of in-situ dual-size TiB2 particles reinforced 6201 aluminum matrix composites

Abstract

The design of high-performance overhead aluminum wires is challenging, due to the intrinsic trade-off of strength-ductility and strength-electrical conductivity (EC). The in-situ halide salt reactions were used to introduce dual-size TiB2 particles into 6201 alloy to obtain out-bound mechanical properties with slight sacrifice of EC. With this strategy, the ultimate tensile strength, elongation after fracture and EC of the 4 wt%TiB2/6201Al composite are 360.9 MPa, 8.27% and 53.5% IACS, respectively, and these properties of the reference 6201 alloy are 325.0 MPa, 7.8% and 56.06% IACS. In the as-cast state, the majority of sub-micron TiB2 particles are segregated at the grain boundaries (termed as GBPs), forming a network pattern. The network is stretched along the rolling direction (RD) during deformation, and the orientation of GBPs is also rearranged from chaotic to a position with c axis nearly normal to the RD. In addition, semi-coherent particle/matrix interface is formed, which play a crucial role in strengthening the matrix. To optimize the EC, neutralization by adding Al–3B master alloy was performed, thus successfully eliminating the detrimental Al3Ti phase and precipitating excessive solute Ti atoms. The results show that not only the EC, but also the strength and ductility maximize at a composition around B:Ti = 2.0.

Keywords

• Metal matrix composites
• Particle reinforcement
• Electrical conductivity
• Grains and interfaces
• Casting