A precipitation-hardened stainless steel alloy comprises, by weight: about 14.0 to about 16.0 percent chromium; about 6.0 to about 7.0 percent nickel; about 1.25 to about 1.75 percent copper; about 0.5 to about 2.0 percent molybdenum; about 0.025 to about 0.05 percent carbon; niobium in an amount greater than about twenty times to about twenty-five times that of carbon; and the balance iron and incidental impurities. The alloy has an aged microstructure and an ultimate tensile strength of at least about 1100 MPa and a Charpy V-notch toughness of at least about 69 J. The aged microstructure includes martensite and not more than about 10% reverted austenite and is useful for making turbine airfoils.