Effect of Mg on the microstructure evolution and mechanical properties of 5%TiB2/Al-4.5%Cu composites

Agglomeration behavior of TiB2 particles in 5%TiB2/Al-4.5%Cu composites (all compositions are in wt.% unless otherwise specified) is studied by adding different content of Mg to improve its strength and ductility, a widely used in-situ molten salt reaction process is used to produce the composites. The results show that addition of Mg could not only significantly segregate TiB2 particles but also further refine the alpha-Al grains and then improve the mechanical properties of the composites on the basis of TiB2 particles. Here, 0.5% Mg is considered the optimum mass fraction for dispersion, refinement, and modification of particles based on the results of investigation. The yield strength (YS), ultimate tensile strength (UTS), elastic Young's modulus (EM), and Vicker's hardness (VHN) of the composites in T6 heat treatment are increased to 375 MPa, 486 MPa, 88 GPa, and 167 HV - an improvement of 21.8%, 16.5%, 20.9%, and 9.4%, respectively, versus the original TiB2/Al-4.5%Cu composite (308 MPa, 417 MPa, 63 GPa, and 153 HV). The elongation of the composite is improved by 20.9%. These merits are mainly attributed to addition of Mg, which increases the surface-spread coefficient of TiB2 particles by reducing the surface tension of the Al melt, thereby improving the wettability.