Microstructure of a CoCrNiTa Alloy System

The effect of tantalum additions to a 40-30-30 CoCrNi alloy has been studied by electron diffraction, transmission and scanning electron microscopy, and energy dispersive x-ray analysis in an attempt to identify the microstructure associated wit£ mechanical properties determined by a previous investigator. Samples were prepared by conventional investment casting techniques and thinned electrolytically in perchloric acid-ethanol solution at 20-35 volts for transmission electron microscopy. This solution also etched the surfaces of the specimens sufficiently to yield good sca ning electron micrographs. Energy dispersive k=ray analysis showed that the castings contain an average of 19% more Ta, 8% more Cr, 9% less Co and 6% less Ni than the weighed amounts.