Microstructure Characterisation and Mechanical Properties of Ti-6Al-4V with Grain Refinement Made by Direct Laser Fabrication

Direct laser fabrication technique (DLF) or laser engineered net shaping (LENS) is one of the additive manufacturing methods for building up large titanium alloy component in aerospace industry. One of the existing issues in the DLF’d titanium alloys is the anisotropic mechanical properties at different directions, which causes difficulties in using DLF’d titanium alloys. The anisotropic mechanical properties are attributed to the presence of large columnar grains. In this study, we investigated into the effect of grain refiner in reducing the mechanical anisotropy in DLF’d titanium alloys. Different amounts of boron were added into Ti-6Al-4V as the grain refiner to make it into pre-alloyed powders. DLF’d Ti-6Al-4V samples with different amount of boron concentrations and different cooling history were manufactured. The correlation between the amount of boron concentrations and cooling history with the mechanical property anisotropy was investigated and established in this study. In study it is found that the anisotropy in DLF’d Ti-6Al-4V can be significantly reduced, which could expand the use of DLF’d Ti-6Al-4V in industry.