Fatigue properties of cast and heat treated Ti-6Al-4V alloy for anatomic hip prostheses.

The intricate shape of Ti-6Al-4V anatomic hip prostheses necessitates the use of casting as a fabrication method, since neither machining, nor forging or powder metallurgial processing are reasonably acceptable. Cast and hot isostatically pressed Ti-6Al-4V, however, has a relatively low ductility and reduced fatigue properties. Appropriate thermal treatments can improve these properties. Specifically, treatments comprising a beta-solutionizing and an aging step yield ductilities similar to the forged and annealed condition, and fatigue properties 11.5% above the non-treated condition. Such treatments produce small alpha-beta platelet colonies with a ragged, tortuous morphology. The reduction of scatter in fatigue strength is the result of the formation of this well controlled microstructure.