A cobalt-nickel alloy composition is described, containing about 20% to about 28% cobalt; about 37% to about 46% nickel; at least about 6% chromium; aluminum; and at least one refractory metal. The total weight of cobalt, aluminum, and refractory metal in the composition is less than about 50% of the total weight of the composition. Moreover, the alloy composition comprises both a (Co, Ni)-gamma phase and an L12-structured (gamma prime) phase. Various components made from the cobalt-nickel alloy composition are also described. Examples include high-temperature machinery and devices, e.g., components of gas turbine engines.