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.

在熔体中添加有效的成核颗粒以实现晶粒细化已成为铸造行业最广泛使用的方法。在这项研究中，利用碳源气体与镁熔体的原位反应制备了一种具有纳米复合结构的新型GNP@MgO颗粒。结果表明，该颗粒能够将Mg-9Al合金的平均晶粒尺寸从130.4μm显着降低至13.1μm，并实现90%的超高晶粒细化效率。细化机制是由于(001) _Al4C3 //(002) _{Mg 的取向关系，Al 4} C ₃相可以作为α-Mg晶粒的异质形核位点。同时，颗粒分布模型表明，MgO颗粒的速度远高于α-Mg晶粒的生长速率。因此，在凝固过程中它被推向晶界附近，有效限制了α-Mg晶粒的长大。_{通过Al 4} C ₃和MgO颗粒的协同调节，实现了显着的晶粒细化效果。这项工作可能为设计镁铝合金高效晶粒细化剂提供新的见解。