Laser-deposited Ti-Nb-Zr-Ta orthopedic alloys.

Abstract

The complex quaternary Ti-35Nb-7Zr-5Ta orthopedic alloy has been successfully deposited from a powder feedstock consisting of a blend of elemental titanium, niobium, zirconium, and tantalum powders, using the laser engineered net-shaping (LENStrade mark) process. In the as laser-deposited form, these alloys exhibit a substantially higher tensile strength as compared with more conventionally processed counterparts of similar composition, while maintaining excellent ductility and a low modulus. Furthermore, the as-deposited alloys appear to exhibit a <001> texture, with a substantially large number of grains of the beta phase aligning one of their <001> axes nearly normal to the substrate or parallel to the growth direction. The microstructure of the as-deposited as well as tensile-tested alloys have been characterized in detail using scanning electron microscopy (SEM), orientation microscopy (OM), and transmission electron microscopy (TEM). Formation of a high density of shear bands, possibly arising from slip localization due to precipitates of the omega phase in the beta matrix, is clearly evident in the tensile-tested sample. The enhanced tensile strength and low modulus in these laser-deposited alloys coupled with the ability to form near-net shape components makes LENS an attractive processing technology for orthopedic implants.