Tailoring the mechanical properties of hypereutectic in situ Al-Mg2Si composites via hybrid TiB2 reinforcement and hot extrusion

Microstructure and mechanical properties of Al-15Mg(2)Si-xTiB(2) hybrid composites in the as-cast and wrought conditions were studied. TiB2 addition led to a significant refinement and modification of primary Mg2Si particles (up to 3 wt% TiB2 addition) via the heterogeneous nucleation mechanism, which improved the as-cast tensile properties. Further additions led to the appearance of coarse needle-shaped Al3Ti particles with the consequent deterioration of tensile properties. Hot deformation by extrusion process and elevated-temperature exposure resulted in the fragmentation, dispersion, and spheroidization of pseudo-eutectic Mg2Si constituents, which led to a significant enhancement of tensile properties. The ultimate tensile strength of the extruded Al-15Mg(2)Si-3TiB(2) composite was 285 MPa with the total elongation of 8%, which revealed a good strength-ductility balance. The corresponding value for the as-cast Al-15Mg(2)Si composite was only 198 MPa%. Accordingly, this study revealed that the presence of optimum amount of TiB2 combined with high-temperature thermomechanical processing could remarkably improve the mechanical properties of the hypereutectic Al-Mg-Si composites in terms of strength-ductility balance, quality index, and tensile toughness.

Automated summary

In this study, the microstructure and mechanical properties of Al-15Mg(2)Si-xTiB(2) hybrid composites in different conditions were investigated. The addition of TiB2 improved the as-cast tensile properties, while further additions resulted in a deterioration of tensile properties. Hot deformation and elevated-temperature exposure enhanced the tensile properties by fragmenting, dispersing, and spheroidizing the pseudo-eutectic Mg2Si constituents. The presence of an optimal amount of TiB2 combined with high-temperature thermomechanical processing significantly improved the mechanical properties of the hypereutectic Al-Mg-Si composites.