Effect of tantalum additions to a cobalt-chromium-nickel base alloy.

The effect of additions of tantalum (Ta) to a 40-30-30 cobalt (Co) -chromium (Cr) nickel (Ni) alloy has been studied for several years at the University of Michigan. Mechanical properties of a series of these alloys have been reported by Mohammed and Asgar.1 Those results showed that an alloy containing 13% Ta would have an ultimate tensile strength of 124,000 psi, a yield strength of 90,000 psi, and an elongation of 10%. There is a sharp change in these properties around 12 to 13% Ta. In the present study, this system was examined by electron diffraction, transmission and scanning electron microscopy, and energy-dispersive X-ray analysis to identify the microstructure associated with these mechanical properties.