Nanoparticle-reinforced Mg matrix composites (NPMMCs) capitalize on the synergistic properties of nanoparticles and Mg matrix, resulting in enhanced mechanical attributes compared to matrix. Nonetheless, effective high-temperature dispersion of nanoparticles remains challenging. This study employs a molten salt dispersant (NaCl-KCl-MgCl₂) effectively mitigating the oxidation and combustion of TiC nanoparticles (TiC_np). Compared with the atmosphere, the molten salt facilitates the pre-dispersion of TiC_np through thermal motion at elevated temperatures, thereby reducing agglomeration between the TiC_np. Simultaneously, the molten salt effectively wets and disrupts the oxide layer on the surface of Mg melt, facilitating the wetting of TiC_np by the Mg melt. The successful incorporation of 3 vol.% TiC_np into the Mg matrix is achieved by utilizing molten salt, and the addition of TiC_np increases the viscosity of mg melt. Further dispersed by ultrasonic dispersion, the unique distribution of TiC_np within ring-like structures was obtained which was attributed to the increase of viscosity. As a configurational distribution, the ring-like TiC_np distribution morphology significantly enhances the mechanical properties of composites, as evidenced by an approximate 50 % increase in compressive strength (UCS).

The addition of effective nucleating particles in the melt to achieve grain refinement has become the most widely used method for the casting industries. In this study, a novel GNP@MgO particle with a nanocomposite structure was prepared by utilizing an in-situ reaction of the carbon source gas with Mg melt. The results showed that the particles can significantly reduce the average grain size of Mg-9Al alloy from 130.4 µm to 13.1 µm, and achieve an ultra-high grain refinement efficiency of 90%. The refinement mechanisms are that the Al₄C₃ phase can act as a heterogeneous nucleation site for α-Mg grains due to the orientation relationship as (001)_Al4C3//(002)_Mg. Meanwhile, the particle distribution model shows that the velocity of MgO particles is much higher than the growth rate of α-Mg grains. Therefore, it is pushed to the vicinity of grain boundaries during solidification, effectively limiting the growth of α-Mg grains. The remarkable grain refinement effect was achieved through the synergistic modulation of Al₄C₃ and MgO particles. This work may provide new insight into designing high efficiency grain refiners for Mg-Al alloys.