TiB2 particulate reinforced magnesium matrix composites were successfully fabricated by adding a TiB2–Al master alloy processed via the flux-assisted synthesis (FAS) reaction into molten magnesium. X-ray diffraction (XRD) analysis and microstructural characterization of the TiB2–Al master alloy revealed the formation and uniform distribution of TiB2 reinforcements. By stirring, magnesium matrix composites with dispersed homogenously TiB2 particles can be obtained. Microstructural characterization of the TiB2/Mg composites revealed retention of hexagonal or rectangular TiB2 particulates with the size of about 1 μm.

The (AlN+Mg2Si)/Mg metal matrix composite was successfully fabricated by adding Si3N4 into Mg-Al alloy. The formation mechanisms of AlN and Mg2Si were analyzed; the effects of synthesizing temperature and holding time were investigated as well.

The effect of the alloying element additions on in-situ chemical reaction to synthesize particulate reinforced TiC/Mg composites was evaluated from the viewpoint of thermodynamics. The influences of alloying elements on the changes of the activity coefficient and the excess free energy in molten magnesium were calculated. The results show that additions, such as Nd, La, Ca, Cu and Zr can promote TiC formation, at the same time hinder the brittle TiAl3 phase formation.

Alloying additions have an important effect on in-situ chemical reaction 4Al+Si3N4=4AlN+3Si to synthesis (AlN+Mg2Si)/Mg composites. Using the Wilson equation and an extended Miedema model, the activity in a multiple-component system can be calculated，and then the Gibbs free energy can be calculated. In final, the influence of alloying element additions on the in-situ chemical reaction at high temperature is investigated from a thermodynamic viewpoint.

No abstract