Metallurgical features of direct laser-deposited Ti6Al4V with trace boron

The variation in the metallurgical characteristics, in terms of microstructure and microhardness, of direct laser deposited Ti6Al4V premixed with trace boron (0.04 wt%) was investigated. A significant improvement in the clad hardness from 390 to 450 HV in Ti6Al4V deposit to 510-600 HV in Ti6Al4V0.04B clad was observed. This was attributed to not only the fine α-Ti laths but also the presence of very hard TiB precipitates formed in the latter sample when compared to the martensitic α′-Ti formed in the former specimen. The high cooling rates experienced during deposition produced an extremely fine and even distribution of TiB.