The superior elevated-temperature mechanical properties of Al-Cu-Mg-Si composites reinforced with in situ hybrid-sized TiCx-TiB2 particles

The Al-Cu-Mg-Si matrix composites reinforced with in situ hybrid-sized TiCx-TiB2 particles with sizes ranging from 20 nm to 1.3 mu m were successfully synthesized using the Al-Ti-B4C reaction system via a method that combined the combustion synthesis and the hot press assisted with hot extrusion. The sizes of the fabricated TiCx and TiB2 particles increased with increasing TiCx-TiB2 content. The hybrid-sized TiCx-TiB2 particles improved the elevated-temperature yield strength (sigma(.2)), the tensile strength (sigma(UTS)), and the fracture ductility (epsilon(f)) of the composites at both 493 K and 573 K. The 40 wt% (TiCx-TiB2)/Al-Cu-Mg-Si composite exhibited superior sigma(.2) (141 MPa), sigma(UTS) (164 MPa), and epsilon(f) (31.2%) at 573 K, with enhancements of 60.2%, 72.6%, and 22.4% compared to the Al-Cu-Mg-Si matrix alloy (88 MPa, 95 MPa, and 25.5%). The improvement of the elevated-temperature mechanical properties for the in situ (TiCx-TiB2)/Al-Cu-Mg-Si composites was attributed primarily to the strengthening effects induced by the hybrid-sized TiCx-TiB2 particles and the theta' precipitation strengthening.