Effect of SiC addition on the microstructure and properties of Ti6Al4V by selective laser melting

Abstract

The fine crystalline behavior of SiC/Ti6Al4V is revealed in this study. Titanium matrix composites (TMCs) with different types, amounts, and morphologies of second phases were prepared in situ by adding different contents of SiC. The grain refinement mechanism of multi-phase synergistic was analyzed, and the synergistic contribution of the in-situ second phases (TiC, Ti₅Si₃, and Ti₃Si) as well as the fine grain organization to the strengthening of the materials was quantitatively evaluated. The results show that the quasi-continuous network structure formed by the in situ TiC and Ti₅Si₃ phases inhibits grain growth and completes the equiaxed transformation of β-grains. Meanwhile, the TiC phase provides a large number of nucleation sites for the α-Ti phase, which promotes the nucleation of the matrix phase. Finally, the aspect ratio of the α phase was reduced from 5.8 to 3.1, while the β grain size was refined from 20.0 to 1.7 µm. The matrix hardness (6.3 GPa) and compressive yield strength (1692 MPa) of TMC were increased by 37% and 67.4% respectively compared with Ti6Al4V. Fine grain strengthening accounted for 71.2% of the total strengthening increase. The load-bearing strengthening caused by TiC, Ti₅Si₃ and Ti₃Si accounted for 6.0%, 11.6% and 3.0% of the total strengthening increase, respectively.