Abstract: Nickel-iron base alloy characterized by controlled thermal expansion coefficient and inflection temperature and by desirable high strength in age-hardened condition has composition specially restricted to overcome detrimental sensitivity to stress-concentrating geometries and aid resistance to long-enduring stress in heated oxidizing atmospheres. The alloy contains, by weight, 34% to 55.3% nickel, up to 25.2% cobalt, 1% to 2% titanium, 1.5% to 5.5% of columbium plus 1/2 the weight percent of any tantalum, up to 1% chromium, not more than 0.2% aluminum and the balance essentially iron.

Abstract: Nickel-iron and nickel-iron-cobalt alloys contain chromium and gamma-prime hardening elements in proportions balanced according to special compositional relationships providing desired thermal expansion, inflection temperature, strength and ductility characteristics, particularly including notch strength needed in machinery and structures subjected in use to varying temperatures and thermal gradients where operating temperatures become elevated above 500.degree. F.