Al-Cu-Mg based alloys (i.e. 2024 alloy) have been widely used in aerospace industry due to their high strength and light weight. However, Al-Cu-Mg based alloys have a significant hot tearing tendency and a serious segregation issue due to their large solidification range. An effective grain refinement can be used to solve the hot tearing and segregation issues. Although the addition of 0.1 wt.% TiB2 (as grain refiner) into Al-Cu-Mg based alloys (regarded as Al-Cu-Mg based composites) can refine grain size down to 200 µm, it is still not enough. In this paper, the addition of 3 wt.% TiB2 (as grain refiner) into Al-Cu-Mg based alloys will be investigated, which can refine grain size down to 50 µm and thereby greatly reduce hot tearing tendency and segregation. Furthermore, additive manufacturing (laser powder bed fusion) was used to produce rods with a diameter of 12 mm and height of 200 mm. The precipitation of Al-Cu-Mg based composites produced by additive manufacturing was also investigated by using transmission electron microscopy (TEM) and atom probe tomography (APT). Three different types of precipitates (Al-Cu (θ) phase, Al-Cu-Mg-Ag (Ω) phase and Mg-Si (β) phase) were observed, which is fully consistent with the case of samples produced by conventional gravity die casting condition. More interestingly, one Mg, Ag-rich layer was observed in the vicinity of Al-Cu (θ) phase. These careful TEM characterizations and quantitative atom probe data analyses give us some hints to design high performance Al-Cu-Mg based composites.