Effect of In Situ 2%TiB2 Particles on Microstructure and Mechanical Properties of 2024Al Additive Manufacturing Alloy

Laser powder bed fusion (L-PBF) is an innovative additive manufacturing method with great potential for fabricating complex geometrical components with integrated functionalities. In the aerospace industry, the Al-Cu-Mg (2024Al) alloy is widely used because of its excellent mechanical properties and low density; however, its disadvantages include low printability and high crack susceptibility. This work investigates the effects of in situ TiB 2 particles on the microstructure and tensile properties of the solution-treated (510oC treat 1 h and then cooling by water) and T6-treated (i.e., solution and aging treatments) L-PBF fabricated 2024Al alloy at room temperature. Equiaxed grains with an average size of approximately 5.8 mu m dominate in the printed 2024Al-2%TiB2 alloy because of the high cooling rate during the L-PBF process and the heterogeneous nucleation effect of the TiB 2 particles. After the T6 heat treatment, many uniformly distributed, fine, and long precipitation strips formed in both the 2024Al and 2024Al-2%TiB2 alloys. The 2024Al-2%TiB2 alloy has ultimate tensile and yield strengths of (458.2 +/- 6.5) and (398.4 +/- 2.7) MPa, respectively; further, it has a maximum elongation of (3.4 +/- 0.4)%. These parameters indicate a substantial improvement in the strength and elongation of the 2024Al-2%TiB2 alloy compared to those of the 2024Al alloy. Furthermore, the mechanical properties of the T6-treated 2024Al2%TiB2 alloy are comparable to those of the wrought T6-treated 2024Al-T6 alloy. The main strengthening mechanisms of the 2024Al-2%TiB2 alloy include solid solution strengthening, dislocation strengthening, grain boundary strengthening, precipitation strengthening, Orowan strengthening, and load-bearing strengthening induced by TiB2 particles. In conclusion, 2024Al-2%TiB2 alloy manufactured using the LPBF method provides excellent printability and room-temperature tensile properties.