Characterization of novel borides in Ti–Nb–Zr–Ta + 2B metal-matrix composites

Metal-matrix composites consisting of a complex quaternary Ti-35Nb-7Zr-5Ta alloy reinforced by borides have been successfully deposited from a powder feedstock consisting of a blend of elemental titanium, niobium, zirconium, tantalum, and, titanium diboride (TiB2) powders, using the laser engineered net-shaping (LENS™)11LENS™ or Laser Engineered Net Shaping is an additive manufacturing process where a directed laser beam is used to melt and deposit powders of desired composition in a layer-by-layer 3D near-net shape fashion. For more information on this refer to D.M.Keicher and J.E. Smugeresky, JOM, 49(5), 51 (1997). ss. The microstructures of the as-deposited composites have been characterized using scanning electron microscopy, orientation microscopy, and, transmission electron microscopy. Both primary and eutectic boride precipitates, exhibiting the orthorhombic B27 structure, are observed in these as-deposited composites. The complex primary borides exhibit an unusual compositional variation within the same precipitate, which has been investigated in detail using site-specific characterization with a transmission electron microscope. The ability to form near-net shape components using the Laser Engineered Net Shaping process makes these laser-deposited composites promising candidates for wear-resistant applications in biomedical implants.