In Situ Fabrication of TiB/Ti-6Al-4V Composites Using Laser Beam Manufacturing Technique: Effect of Submicron TiB2

A titanium matrix composite consisting of in situ-generated TiB whiskers in the Ti-6Al-4V matrix was fabricated by adding submicron TiB2 particles to Ti-6Al-4V powder in proportions ranging from 0.05 wt.% to 1.0 wt.% TiB2, and the resulting powder were used to fabricate samples of the TiB/Ti-6Al-4V composite using the laser powder bed fusion (LPBF) technique. The influence of submicron TiB2 particles on the microstructure, wear, and mechanical properties was thoroughly examined. The microstructural analysis revealed that for 0.05-to 0.2-wt.% TiB2 addition, in situ formation of nanosized TiB whiskers occurs in the form of clusters which are distributed uniformly throughout the Ti-6Al-4V matrix, whereas for 0.5- to 1.0-wt.% TiB2 addition, the TiB whiskers form a continuous network. The size of the TiB whiskers ranges in diameter from 25 nm to 40 nm, and length from 150 to 600 nm. The inclusion of TiB2 particles dramatically alters the as-built microstructure, causing a transition from martensitic to bimodal. The dual mechanism for microstructure refinement has been explained. Wear tests showed significant improvement in the wear performance as a result of the formation of hard nanosized TiB whiskers that were strongly attached to the Ti-6Al-4V matrix.