A new approach for improving the elevated-temperature strength and ductility of Al-Cu-Mg-Si alloys with minor amounts of dual-phased submicronanosized TiB_2-TiC particles

摘要

At high temperatures, the weakened strength and decreased ductility of Al alloys limit their industrial applications. (TiB2-TiC)/Al-Cu-Mg-Si composites were synthesized by adding in situ dual-phased and bimodal-sized (TiB2-TiC)/Al master alloys to molten Al-Cu-Mg-Si alloys. The addition of minor amounts of TiB2 and TiC particles (0.05 and 0.1 wt%, respectively) effectively refined the alpha-Al grains and theta' and Q' precipitates and increased the elevated-temperature strength and uniform elongation of the Al-Cu-Mg-Si alloys. The 0.1 wt% (TiB2-TiC)/Al-Cu-Mg-Si composite showed the best yield strength (279 MPa), ultimate tensile strength (366 MPa), and uniform elongation (10.6%) at 493 K, with enhancements of 9.4%, 15.1%, and 24.7% compared to the Al-Cu-Mg-Si matrix alloy (255 MPa, 318 MPa, and 8.5%). The simultaneous increases in the elevated temperature strength and ductility of the composites were attributed to the strengthening effects of the bimodal sized TiB2 and TiC particles, theta' and Q' precipitation strengthening, and the refined partial recrystallization microstructure.