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 TiB 2 particles to Ti-6Al-4V powder in proportions ranging from 0.05 wt.% to 1.0 wt.% TiB 2 , 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 TiB 2 particles on the microstructure, wear, and mechanical properties was thoroughly examined. The microstructural analysis revealed that for 0.05-to 0.2-wt.% TiB 2 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.% TiB 2 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 TiB 2 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.