Additive layer manufacturing of titanium matrix composites using the direct metal deposition laser process

Abstract

Titanium Matrix Composites (TMC's) containing various volume fractions of (TiB+TiC) particles have been deposited from powder feedstocks consisting of a blend of pre-alloyed (Ti-6Al-4V+B4C) powders, using the direct metal deposition (DMD) laser process and the in-situ chemical reaction 5Ti+B4C→4TiB+TiC. Process optimization has allowed to obtain a homogeneous distribution of tiny TiB whiskers within the Ti-6Al-4V α/β matrix, with a full solubilization of C for low B4C contents (0.5 wt% and 1.5 wt%), and the formation of a small amount of globular TiC particles at higher B4C content (3%). Comparisons with Ti-6Al-4V DMD walls revealed a substantial grain refinement on TMC's due to enhanced grain nucleation on TiB whiskers, even for low B4C contents. Last, mechanical investigations indicated an increase of 10–15% of Vickers hardness, and a constant 10% increase of Young modulus on a large temperature range (20–600 °C) for all B4C content