Effect of tungsten additions on the mechanical properties of Ti-6Al-4V

The alloy Ti-6Al-4V was modified by addition of 10 wt.% tungsten through powder metallurgy. Depending on the initial W powder size, different materials were formed after powder densification: (i) "alloys" for fine (0.7 and 2 μm) W powders which were almost completely dissolved in the Ti-6Al-4V matrix; (ii) "alloyed composites" for intermediate (12 and <45 μm) W powders which were partially dissolved; (iii) and "composites" for coarse (<250 μm) W powders which were nearly un-dissolved. In all cases, tungsten strengthens Ti-6Al-4V, but much more so when dissolved in the matrix than as a second phase. Ductility was not affected by W additions for the fully-dissolved alloys, but was reduced in the case of composites with W particles, which exhibited fracture or pull-out from the matrix. Flaw sensitivity was apparent from strain hardening being much lower in tension than in compression, and from a much reduced ductility exhibited by one specimen with residual porosity.