Effects of nanosized TiCp dispersion on the high-temperature tensile strength and ductility of in situ TiCp/Al-Cu-Mg-Si nanocomposites

In situ TiCp/Al-Cu-Mg-Si nanocomposites were prepared in Al-Ti-C systems with different carbon sources (pure carbon black, mixed carbon source (50 wt% CNTs + 50 wt% carbon black) and pure CNTs) via a combination of the combustion synthesis, hot press and hot extrusion methods. The in situ TiCp/Al-Cu-Mg-Si nanocomposites synthesized by the mixed carbon source obtained the most uniform distribution of nanosized TiCp, highest yield strength (σ0.2) and tensile strength (σUTS) and best fracture strain (εf). The 30 vol% TiCp/Al-Cu-Mg-Si nanocomposite synthesized by the mixed carbon source showed superior σ0.2 (217 MPa), σUTS (251 MPa), and εf (17.7%) at 533 K, which were respectively 4.3%, 4.1% and 136% higher than those of the nanocomposite synthesized by pure C black (208 MPa, 241 MPa and 7.5%) and respectively 3.8%, 1.6% and 88.3% higher than those of the nanocomposite synthesized by pure CNTs (209 MPa, 247 MPa and 9.4%). The superior high-temperature tensile strength and ductility of the nanocomposites prepared by the mixed carbon source were attributed to the homogeneous distribution of nanosized TiCp. The strengthening of the nanosized TiCp and θ′ precipitates was the main strengthening mechanism of the in situ TiCp/Al-Cu-Mg-Si nanocomposites at high temperatures.