Investigation on the high strength and improved creep behavior of in-situ (Al2O3+ZrB2)/7055 Al nanocomposites

In this paper, 7055 Al composites reinforced by Al2O3 and ZrB2 nanoparticles were fabricated by in-situ reaction. The adhesion (Wad) of the ZrB2/Al interface was 3.91 J/m2 while the adhesion at the Al2O3/Al interface was 3.69 J/m2. At room temperature and high temperature up to 523 K, yield strength (YS), ultimate tensile strength (UTS), and elongation (EI) in (Al2O3+ZrB2)/7055 Al composites reached up to 595 MPa, 710 MPa, 19% and 371 MPa, 435 MPa, 24%, respectively. The combined strengthening effect produced by Al2O3 and ZrB2 nanoparticles was found to be stronger than that of the individual ZrB2 particles and the matrix. In addition, the steady creep rate of the (Al2O3+ZrB2)/7055 Al composites were the lowest, constituting only 3-14% of the matrix and 5-68% of the ZrB2/7055 Al composites. The true stress exponents in the matrix and composites were 5, indicating a dominative dislocation climbing mechanism. Both the promotion of precipitation nucleation and the precipitation-coarsening inhibition during the creep process at the interfaces between the matrix and nanoparticles were discussed. Additionally, deformed and fragment mechanisms and the creep resistance mechanism were elucidated.